Air Duct Elbow Loss. Calculation of pressure loss in elbows on ventilation ducts. Fill in the form below. Wid. (W)/Heig. (H) Calculation of local losses in elbows in ventilation ducts.Sep 30, 2023 · Duct load calculation involves determining the heating or cooling load that a duct system must handle. It includes factors like air temperature, humidity, and the area being served. The calculation is complex and is typically done using specialized software. ρ = 999.7 kg/m³. Find the dynamic viscosity: µ = 0.001308 kg/ (m · s) Compute the product of the density of water, the velocity of the flow, and L: ρ × u × L = 249.925 (m · s)/kg. Divide the result by the dynamic viscosity to find the Reynolds number: ReD = 249.925/0.001308 = 191,074 The flow is likely turbulent.ρ = 999.7 kg/m³. Find the dynamic viscosity: µ = 0.001308 kg/ (m · s) Compute the product of the density of water, the velocity of the flow, and L: ρ × u × L = 249.925 (m · s)/kg. Divide the result by the dynamic viscosity to find the Reynolds number: ReD = 249.925/0.001308 = 191,074 The flow is likely turbulent.Download duct static pressure calculator excel sheet XLS. Free spreadsheet program for air duct friction loss calculation. Download Free MEP Calculation Excel Sheets, AutoCAD Drawings, and Training Courses for HVAC, Firefighting, Plumbing and Electrical Systems Design.The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ...The pressure drop across a valve can be calculated using the valve’s Cv (flow coefficient) value and the flow rate. The equation is: Pressure Drop (psi) = (Cv × Q^2) / (SG × ΔP) where Q is the flow rate (in gallons per minute), SG is the specific gravity of the fluid, and ΔP is the pressure drop across the valve.How Much Does an HVAC Replacement Cost in 2024? Average Cost Range: $6,465 - $11,877. Use the calculator below for a more accurate local estimate. Use Modernize's 2024 cost calculator to get accurate HVAC replacement cost. Get local price ranges by zipcode for cooling, heating or both!A major friction loss diagram for air ducts - Imperial units ranging 10 - 100 000 cfm. Air Ducts - Major Friction Head Loss, Online Calculator Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units. Air Ducts - Sizing Required duct area vs. air flow. Air Ducts - Velocity ...CFM (10×12 Duct, 500 FPM) = 500 FPM × 10 Inches × 12 Inches / 144 = 416.67 CFM. We can see that the 10×12 duct generates 416.67 CFM of airflow at 500 FPM air speed. Now, we did a huge amount of calculations for these rectangular ducts at 1 FPM, 500 FPM, and 2000 FPM, and gathered all the results in this feet per minute to cubic feet per ...In April 2024 the cost to Install a Duct starts at $12.13 - $21.39 per linear foot. Use our Cost Calculator for cost estimate examples customized to the location, size and options of your project.. To estimate costs for your project: 1. Set Project Zip Code Enter the Zip Code for the location where labor is hired and materials purchased.. 2.DUCTULATOR. Sizing air ducts is essential task for HVAC Engineers, it requires quick tool to aid HVAC designer to determine air duct dimensions while drafting AC layouts. DUCTULATOR Software, uses two methods to size air ducts based on velocity or static regain method, taking into account the air properties at given temperature and elevation ...A good HVAC duct sizing rule of thumb is to measure rooms in your home, the necessary airflow rates, and friction loss rate. Using these numbers you can calculate the appropriate HVAC duct size. For example, a one-to AC system typically uses 10-inch ducts, while a 4-ton AC system requires 18-inch ducts. There are several variables to …Purpose and Learning Objectives. The purpose of this presentation is to introduce new and optimized techniques for designing high performing VAV systems at minimal cost. At the end of this presentation, you will be able to: Size VAV duct mains cost effectively. Select VAV boxes for minimum life cycle cost.Ducting Calculators and Air Volume Converter. Nordfab can offer technical assistance with determining whether our ducting is best for your application and with designing duct installations. Please contact us with your requirements. Input CFM Input Velocity (FPM) Ideal Round Duct Diameter Duct Friction in Straight Duct. Calculate.Dec 20, 2016 · 20 Dec 2016; Atlanta; New Duct Sizing Calculator Available. Media Contact: Allen Haynes 404.446.1677 [email protected]. ATLANTA (Dec. 20, 2016) – A new duct sizing calculator from ASHRAE and the Air Distribution Institute (ADI) allows HVAC air distribution system designers to more accurately size ducts, especially flex ducts under varying amounts of compression, based on research results. Duct thickness. Refers to the thickness of the goods on the actual duct. Duct density. Refers to the density of the material from which the duct is made. Duct weight. Refers to the weight of the current duct per meter. Media density. Refers to the density of the medium flowing through the actual duct. Set to air in the initial position. Media ...The Ductulator - Duct Sizing Calculator is a hand held rotating calculator used for sizing supply and return duct systems using the equal friction design method. This accurate, easy-to-use duct size calculator includes scales for friction loss per unit length, air volume, air velocity, round duct diameter and rectangular duct diameters.Air Duct Elbow Loss. Calculation of pressure loss in elbows on ventilation ducts. Fill in the form below. Wid. (W)/Heig. (H) Calculation of local losses in elbows in ventilation ducts.The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ...The velocity reduction method can be used when sizing air ducts. Equivalent Diameter - Rectangular vs. Circular HVAC Ducts Rectangular equivalent diameter for air flows between 100 - 50000 cfm. Fluid Flow - Equivalent Diameter Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI ...The head loss calculator below is based on formula (1) : Air Volume Flow - q - (cfm) Equivalent duct diameter - d e - (inches) Duct Length - (feet) Equivalent Diameter - …By knowing how to calculate static pressure in air duct systems, you can determine that the right push of air counteracts the resistance in airflow. In a static pressure calculation, we are looking for the push of air to exceed the resistance. Otherwise, the system won't be able to circulate air throughout the ducts.Calculation Method. Static Pressure Loss [inW/100ft] Air Flow [CFM] 3000 FPM. Round Duct Air Velocity. Infinity FPM. Rectangular Duct Air Velocity. 0.00049 Absolute Roughness [Foot] 14.42.Highlights. Your air ducts deliver cool and hot air throughout your home. There are sheet metal, fiberglass-lined, fiberboard, and flexible ducts. Some signs you need a cleaning include dirty vents and a pest infestation. Air duct cleaning costs $380 on average and ranges between $270 to $490.Jan 14, 2012 · The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ... Diameter of Air Duct Sizing =√ ( (576 × 8) / (3.14 × 15)) = 9.8911 inch. Online ducting calculator to find the diameter of duct size. Sizing of air duct can be done using Velocity Method, Constant Pressure Loss Method and Static Pressure Recovery Method.Mar 4, 2023 · Duct Sizing Calculator. The duct sizing calculation involves determining the proper ductwork size needed for an HVAC system. The formula used in this calculation is Q=VA, where Q is the airflow rate, V is the air velocity, and A is the area of the duct. To calculate the kinematic viscosity of air at pressure 1 bar (105 Pa) and 50 °C, enter a few details into the kinematic viscosity of air calculator: Convert the temperature in Celsius to kelvin: T = 273.15 K + 50 = 323.15 K. Calculate the density of the air from the ideal gas law: ρ = P/ (RT) = 105 Pa/ (287.05 J/kg·K × 323.15 K) = 1.078 kg/m3. The velocity of an air duct with area 16 sq.ft and air flow of 10 CFM would be : V = 10 / 16 = 0.625 FPM. When converted to FPS, it is 0.0104 FPS. Air duct also termed as ductulator is a passage that is used to provide fresh air into rooms, buildings etc., Air ducts may be in circular, square and in rectangular shapes. Download duct static pressure calculator excel sheet XLS. Free spreadsheet program for air duct friction loss calculation. Download Free MEP Calculation Excel Sheets, AutoCAD Drawings, and Training Courses for HVAC, Firefighting, Plumbing and Electrical Systems Design.Lindab Vent Tools app streamlines ventilation system calculations with practical tools for HVAC professionals. This handy app offers a collection of practical calculation tools for the HVAC industry, including duct dimensioning, pressure drop, airflow, and offset calculation for Lindab's products. The app also includes a k-factor calculator for versatile use …Mar 4, 2023 · Duct Sizing Calculator. The duct sizing calculation involves determining the proper ductwork size needed for an HVAC system. The formula used in this calculation is Q=VA, where Q is the airflow rate, V is the air velocity, and A is the area of the duct. How to design a duct system. In this video we'll be learning how to size and design a ductwork for efficiency. Includes a full worked example as well as usin...To adequately calculate the speed of air in ducts, we have to primarily calculate the cross-section of the duct. Shape-wise, ducts can be: Round. The area of round flex ducts is calculated as π*R 2 where R is the radius of the duct. Example: 10-inch round duct has a radius of 5 inches.The Duct Size Calculator is a quick reference tool for approximating duct size and equivalent sizes of sheet-metal duct and flexible duct. A new duct-sizing calculator from ASHRAE and the Air Distribution Institute (ADI) allows HVAC air-distribution-system designers to size ducts more accurately, especially flex ducts under …Apr 6, 2024 · The Duct Size Calculator is a quick reference tool for approximating duct size and equivalent sizes of sheet-metal duct and flexible duct. A new duct-sizing calculator from ASHRAE and the Air Distribution Institute (ADI) allows HVAC air-distribution-system designers to size ducts more accurately, especially flex ducts under varying amounts of ... Diameter of Air Duct Sizing =√ ( (576 × 8) / (3.14 × 15)) = 9.8911 inch. Online ducting calculator to find the diameter of duct size. Sizing of air duct can be done using Velocity Method, Constant Pressure Loss Method and Static Pressure Recovery Method.Duct Calculator - CDI Curbs. Air Duct Calculator. Flexible Duct Friction Loss Calculator. 1. Enter Friction Loss Per 100' of duct (inches of water), Duct Airflow (CFM), Duct Length … Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units. The major loss, or friction loss, in a circular duct in galvanized steel with turbulent flow can for imperial units be expressed. Δh = 0.109136 q 1.9 / d e 5.02 (1) where. Δh = friction or head loss (inches water ... Air Duct Calculators (Ductulator) 2/5. Watch on. This handy little device allows you to size your new air duct, and better understand what to expect from existing duct work. A Ductulator helps you properly size your ducts, estimate air loss, find the round or rectangular duct equivalent, and determine velocity. It can prevent some costly errors ... Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units. The major loss, or friction loss, in a circular duct in galvanized steel with turbulent flow can for imperial units be expressed. Δh = 0.109136 q 1.9 / d e 5.02 (1) where. Δh = friction or head loss (inches water ... October 9, 2023 by GEGCalculators. The size of a return air duct should generally be based on the HVAC system’s capacity. A common rule of thumb is to aim for approximately 400-450 CFM (cubic feet per minute) of airflow per ton of HVAC capacity. For example, a 2-ton system might require a return duct with a size of around 16 inches in diameter.The calculation methodology behind the Duct Size Calculator is straightforward: Duct Size (square inches) = Airflow in CFM / 800 feet per minute. This formula simplifies the process of understanding the correlation between airflow and the necessary duct dimensions. See also Expansion Valve Capacity Calculator Online.Mar 4, 2023 · Duct Sizing Calculator. The duct sizing calculation involves determining the proper ductwork size needed for an HVAC system. The formula used in this calculation is Q=VA, where Q is the airflow rate, V is the air velocity, and A is the area of the duct. Enter the air flowrate in litres/second (can change to cubic metres/second by use of drop-down to the right of the input) Enter an internal duct diameter (this can be any number, it doesn’t need to be standard duct size) To get an idea of the equivalent rectangular duct size, adjust the aspect ratio. Note that only aspect ratio up to 5:1 are ... The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ...Jul 22, 2022 · Step 1: CFM – System Size & Blower Size. Sizing an HVAC System. Step 2: Maximum Friction Rate. Friction Rate and Ductwork Length. What is TEL? Step 3: Maximum Velocity. Summary of Ductwork Sizing Factors. Our Recommendation. The Pick HVAC Ductwork Calculator. The smallest return air grille is usually starts at 4 inches by 4 inches. So, the next corresponding return air grille size includes 4×6, 6×6, 6×4, 8×6, 4×8 and so on. The largest return air grille is typically stops at 48 inches by 24 inches. Here are some examples of a standard return air grille: 4×4. 6×6. The Digitized Ductulator is a free online calculator for sizing HVAC ducts. Use it in one of two ways; either enter the duct size to find the equivalent CFM, or input the CFM to find the right size of rectangular, round or flex duct. Click here to use the Ductulator. Use the right size duct. Duct that's too big, or too small can cause problems ... The average cost to replace ductwork is $1,400 to $5,600, depending on the home's size. Air duct replacement costs $25 to $55 per linear foot or $270 to $500 per duct for a crawl space, attic, or basement. New ductwork installation costs $2,400 to $6,600 for a house without HVAC ducts. Cost to replace ductwork by house size - chart.Precise Calculations: Learn special techniques for superior installation, calculating duct sizes and friction rate. Reduce Hot & Cold Spots: Master duct system balancing to minimize temperature fluctuations. *This class qualifies for 8 hours of NATE continuing education credits. Program Price: $399. Premier Dealers: $319* (20% discount)This article provides information on how to use the Ductwork Calculator for air flow CFM, friction loss and velocity. It explains the process of duct sizing diameter with accurate results when the right information is plugged into it. The article also gives a detailed explanation of each step in the process and what data … See moreAIR DUCT CALCULATOR : by Michael J. Rocchetti PE Mechanical Engineer . Metric Units. Flow rate M^3/S: Velocity M/S: Pressure Pascals: Temperature C: Length Meter: Duct Material: Uncoated Carbon Steel: PVC Plastic Pipe (smooth) Aluminum (smooth) galvanized steel (medium smooth) galvanized steel (average smooth) fiberglass duct …The average cost to replace ductwork is $1,400 to $5,600, depending on the home's size. Air duct replacement costs $25 to $55 per linear foot or $270 to $500 per duct for a crawl space, attic, or basement. New ductwork installation costs $2,400 to $6,600 for a house without HVAC ducts. Cost to replace ductwork by house size - chart. All Duct Calculator. An inclusive air duct calculator for diameter, velocity, CFM, and pressure drop of various types of duct. It will also determine round duct equivalents for rectangle, flat oval, and elliptical (flattened round) duct. Duct roughness and air properties are adjustable and includes a metric option. Open Calculator. Air Duct Calculators (Ductulator) 2/5. Watch on. This handy little device allows you to size your new air duct, and better understand what to expect from existing duct work. A Ductulator helps you properly size your ducts, estimate air loss, find the round or rectangular duct equivalent, and determine velocity. It can prevent some costly errors ...Duct Calculator Elite https://apps.apple.com/us/app/duct-calculator-elite/id665701601Instructions. (Input information may generally be be obtained from design documents or field measurements) Line 1. Enter the temperature of the air entering the duct. Line 2. Enter the ambient temperature (the average temperature of the air surrounding the duct) Line 3. Enter the flow rate of the air carried by the duct in cubic …ρ = 999.7 kg/m³. Find the dynamic viscosity: µ = 0.001308 kg/ (m · s) Compute the product of the density of water, the velocity of the flow, and L: ρ × u × L = 249.925 (m · s)/kg. Divide the result by the dynamic viscosity to find the Reynolds number: ReD = 249.925/0.001308 = 191,074 The flow is likely turbulent.Using the chart, you’ll see that for a 12” round flex duct, maximum CFM is 480 CFM or 500 CFM depending on the friction rate. Duct size for 115 CFM. Find the CFM closest to 115 in the table above. It will be found in different columns depending on the friction rate. If there isn’t an exact match, go up to the duct size.The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ... For 1000 CFM, we need 1650.12 FPM to 11,459.16 FPM, if we use 4-10 inch round ducts. This is quite an enormous air velocity (11,459.16 FPM is equal to 130 miles per hour (mph)). Now, let’s have a look at the 2nd part for rectangular air ducts, starting with the 2nd calculator: Section 5 - Air Distribution System Design This section provides an executive overview of duct system design procedures, additionally covering the use of a branch take off fitting at the end of a supply air trunk duct. Section 6 - Duct Sizing Calculations This section covers the duct system design procedures in detail.Aug 26, 2023 · About this app. This app is developed to Calculate Duct Size Required with available CFM & FPM. This app calculate Both Rectangular and Round Duct Sizes in Inches. This App is also Calculate Air Flow rate in CFM and this app is also calculate in Air Velocity in FPM. The application is designed for engineers HVAC working in the field of design ... The Duct Sizing Calculator is a hand held sliding calculator used for sizing supply and return duct systems using the equal friction, or velocity reduction design method. Front of calculator includes scales for friction, velocity, round duct size, weight per linear foot of round duct, surface area in square feet per lineal foot of round duct ... Adjustable Absolute Duct Roughness. If selected, Flexible roughness is 0.003 ft when. straight and fully stretched tight at 0% compression. (adjusted at other compressions), otherwise the. original method of constant 0.01 ft roughness is used. Use ASH RAE 2013 Flex Compression. A duct size calculator, commonly known as a ductulator, depends on factors like the size of the space you’re heating or cooling, air flow …This tool will calculate the velocity in any units from the specified volumetric flow rate of a substance flowing through a rectangular duct of a defined width and height. For each new calculation a unique conversion scale will be generated for the range of volumetric flow rates and flow speeds for the length and width specified. FormulaAIR DUCT CALCULATOR : by Michael J. Rocchetti PE Mechanical Engineer . Metric Units. Flow rate M^3/S: Velocity M/S: Pressure Pascals: Temperature C: Length Meter: Duct Material: Uncoated Carbon Steel: PVC Plastic Pipe (smooth) Aluminum (smooth) galvanized steel (medium smooth) galvanized steel (average smooth) fiberglass duct …CFM (10×12 Duct, 500 FPM) = 500 FPM × 10 Inches × 12 Inches / 144 = 416.67 CFM. We can see that the 10×12 duct generates 416.67 CFM of airflow at 500 FPM air speed. Now, we did a huge amount of calculations for these rectangular ducts at 1 FPM, 500 FPM, and 2000 FPM, and gathered all the results in this feet per minute to cubic feet per ...PRODUCT DETAILS. AIR DUCT SLIDE RULE CALCULATOR. Size: 4"x9.25". Material: Heavyweight coated calculator board. Production: Each order is custom manufactured with your company information and in your choice of colors. AIR DUCT WIZARD DUCTULATORS. Size: 8.5"x11" card with a 7.25" wheel. Materials: Heavyweight coated … Air Duct Calculator/Ductulator with Sleeve. 3.9 out of 5 stars 14. $14.70 $ 14. 70. FREE delivery Jun 30 - Jul 6 . Flexible Duct Friction Loss Calculator/Flex Duct ... Free HVAC Duct Sizing - in SI/Metric or US/Imperial units. Welcome to CalcuDUCT - the quick and easy way to size ducts for any HVAC application.The Ductulator - Duct Sizing Calculator is a hand held rotating calculator used for sizing supply and return duct systems using the equal friction design method. This accurate, easy-to-use duct size calculator includes scales for friction loss per unit length, air volume, air velocity, round duct diameter and rectangular duct diameters.Using the chart, you’ll see that for a 12” round flex duct, maximum CFM is 480 CFM or 500 CFM depending on the friction rate. Duct size for 115 CFM. Find the CFM closest to 115 in the table above. It will be found in different columns depending on the friction rate. If there isn’t an exact match, go up to the duct size.Cleaning helps not only remove them, but may also remove blockages that can help make your system run more efficiently. Keep reading to learn more about the cost of duct cleaning services. 2024 Duct Cleaning Costs. Calculate local project costs by entering your zip code. Typical Price Range. $ 450 - $ 1,000.Best prices guaranteed. We match other Aussie retailers*. Use our sizing calculator below to determine the minimum size required for your room or house. Remember for ducted systems only include the air conditioned spaces, exclude areas like …At 350-400 CFM per 12,000 BTUs of heating capacity, there’s enough airflow to circulate heated air through supply ducts and pull cool air back to the furnace or air handler through the cold air returns. A 3-ton unit, or 36,000 BTUs, would need a blower capable of moving 3 x 350-400 CFM, so a total of 1,050 to 1,200 CFM.
Calculation of pressure drops of flowing liquids and gases in pipes and pipe elements (laminar and turbulent flow). New version of Online Calculator is available: www.pressure-drop.online. Pressure Drop Software for Excel: Druckverlust Software …. Sf to san diego
JP Lamborn Co. ( JPL ) began producing flexible air ducts in 1961. Today the company operates four state-of-the-art manufacturing facilities and is the largest family-owned flexible air duct manufacturer in North America. JPL’s core values of manufacturing high-quality products, providing excellent service, innovation, and strong business ...DUCTULATOR. Sizing air ducts is essential task for HVAC Engineers, it requires quick tool to aid HVAC designer to determine air duct dimensions while drafting AC layouts. DUCTULATOR Software, uses two methods to size air ducts based on velocity or static regain method, taking into account the air properties at given temperature and elevation ...Jul 22, 2022 · Step 1: CFM – System Size & Blower Size. Sizing an HVAC System. Step 2: Maximum Friction Rate. Friction Rate and Ductwork Length. What is TEL? Step 3: Maximum Velocity. Summary of Ductwork Sizing Factors. Our Recommendation. The Pick HVAC Ductwork Calculator. Imperial Equation. Determine the following formula, which can be used to calculate the air duct velocity: V = 0.408 Q/D 2. Components. = Air velocity inside the duct (feet/s) = Air …The pressure drop across a valve can be calculated using the valve’s Cv (flow coefficient) value and the flow rate. The equation is: Pressure Drop (psi) = (Cv × Q^2) / (SG × ΔP) where Q is the flow rate (in gallons per minute), SG is the specific gravity of the fluid, and ΔP is the pressure drop across the valve.ADI DUCTULATOR. Based on research conducted by Texas Tech University as well as Tennessee Tech University, to study the efect of compression in flexible duct on air flow efficiency, ADI created the Ductulator. This Duct Size Calculator's data is based on flexible duct laying in a straight line on a level surface,and nearly fully stretched (4% ...Example - Calculate Reynolds Number. A Newtonian fluid with a dynamic or absolute viscosity of 0.38 Ns/m 2 and a specific gravity of 0.91 flows through a 25 mm diameter pipe with a velocity of 2.6 m/s .. Density can be calculated from the specific gravity of the fluid and the density of the specific gravity reference water 1000 kg/m 3 - as. ρ = 0.91 (1000 …Imperial Equation. Determine the following formula, which can be used to calculate the air duct velocity: V = 0.408 Q/D 2. Components. = Air velocity inside the duct (feet/s) = Air …mdot = Q / (cp x Δt) Calculate air mass flow rate from cooling load.The equivalent diameter of a rectangular tube or duct can be calculated as (Huebscher) de = 1.30 (a b)0.625/ (a + b)0.25(1) where. de = equivalent diameter (mm, inches) a= length of major or minor side (mm, inches) b= length of minor or major side (mm, inches) Hydraulic diameter - the "characteristic length" used to calculate the dimensionless ... A rectangular 6×6-inch duct has an airflow of 110 CFM. Bigger 6×12-inch ducts can handle 270 CFM airflow. The bigger the crosssection of ducts, the bigger CFM; that’s pretty obvious. The smallest 6×4 ducts can handle 60 CFM airflow. The biggest 42×12 ducts with 504 sq inch crosssection can handle 3000+ CFM airflow. A simple volume unit converter to convert air flow volumes from ... Calculate the equivalent size of spiral ducting when you have only been given the rectangular duct dimension (it works the other way also) Open the ES Calculator. System Pressure Calculator. The System Pressure Calculator helps you work out the resistance in pascals that ....