Round to rectangular duct conversion Duct Dimensions: Enter the diameter for round ducts or the width and height for rectangular ones in inches. This conversion is essential when space constraints CFM (Rectangular Ducts) = FPS × Duct Width (Inches) × Duct Height (Inches) × 60 / 144. 4 Equivalent Diameter . That means that if you are working with a rectangular duct or a flat oval duct, you will need to come up with the equivalent circular duct size if you are using some other cross sectional shape, like rectangular duct or flat oval duct. 3 rectangular duct. This is a handy tool when deciding what size duct you want to use for your application. 25 m3/min. Just use the proper transition pieces. a = length one side of duct, in. 625 / (a+b) 0. ) Round Duct Diameter for Equivalent Pressure Loss at Standard Conditions Calculate Dec 31, 2024 · Ducts: For straight runs, duct TEL or effective length is the same as length. Use a 10 * 12 Using Equivalent Ducts Mode. 250] a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) De= circular equivalent of rectangular duct for equal friction and capacity (inch) Example : convert rectangular duct 22x12 to equivalent round. 3 The Concept of Duct Yes, the Ductulator is designed precisely to calculate the equivalent sizes for both a rectangular and a round duct. com Apr 6, 2025 · 2. 1 ENTRIES 1-1 Duct Mounted in Wall (Hood, Nonenclosing, Flanged, and Unflanged) CONVERSION CHART: RECTANGULAR TO EQUIVALENT ROUND De = 1. 25 where, May 17, 2023 · Hi Dave, the simplest idea here is that the cross-section of the rectangular duct and round duct should be the same. 55. 1 Equal friction method . b = length adjacent side of duct, in. 3 (ab) 0. is only 1-2" to make the transition from round to rectangular Transition, Round to Rectangular, Supply Air Systems. 21. 30 \times \frac{(a \ Aug 10, 2018 · The table below can be used to compare equivalent diameters for rectangular and round circular ducts , ductwork sizing, friction loss, sheet metal gauges, etc. Reference: HVAC EQUATIONS, DATA, AND RULES OF THUMB Definition: This calculator computes the equivalent round duct diameter (\( D_e \)) for a rectangular duct with equal flow, resistance, and length. ) Input Rectangle Duct Depth (in. A rectangular duct and round duct that have the same pressure drop per 100 feet, are what we call equiv Rectangular sheet metal duct = . 3 A 12″ round duct = 10 * 11. 1 in. 3 Oval Ducts . DUCT SHAPES . 3 The Concept of Duct Use the following formula to change the shape of a duct from round to square: Area of a circle = πr² Area / length = width. The DFDB includes more than 220 round, rectangular, and flat oval fittings. How Does the Calculator Work? Oct 2, 2020 · Similar to the previous square to round tap above, this fitting is used on the run instead of tapping into the side of the duct. Diameter: Nov 15, 2023 · Once the cross-sectional area A of the round duct is calculated, finding the equivalent rectangular duct size involves determining the width W and height H using the relationship A=W×H. Then, the air velocity is also limited at 1500 fpm and below. Converting rectangular ducts to round sizes is a crucial step in various engineering and architectural applications. e. The equivalent diameter is the diameter of a circular duct or pipe that gives the same pressure loss as an equivalent rectangular duct or pipe. 250] a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) De= circular equivalent of rectangular duct for equal friction and capacity (inch) Source: 2001 ASHRAE Fundamentals, p. It will also convert rectangular to flat oval. 9 inches. 3. Aug 12, 2021 · The area of a rectangle is the width (W) of the rectangle multiplied by the length (L), while that for a round duct is πD 2 /4, where D is the diameter of the duct. IN (rounded) 113 / 10 = 11. DUCT SIZING . HVAC Systems & Components. 5. Based on the duct design chapter of the ASHRAE Handbook of Fundamentals, the equivalent diameter of a rectangular duct is calculated using the below formula: D e = 1. A round shape results in lower pressure drops and less fan horsepower to move the air and, consequently, smaller equipment. Major Axis (in) Minor Axis (in) 6: 8: 10: 12: 14: 16: 18: 20: 22: 24: 26: 28: 30 Printable, Downloadable Rectangular and Round Duct Sizes Chart, Table. Next, the rectangular duct ratio must not exceed 1:4. The equivalent round size of a rectangular duct is essential for determining the airflow, pressure drop, and overall performance of the system. 250 Where: D Convert Round Duct Size to Rectangular Duct Size for equivelant airflow. Your One Stop Shop for all your HVAC needs. To Calculate Rectangular to Round: table 6 - circular equivalent diameter,* equivalent area and duct class of rectangular ducts for equal friction table 6 - circular equivalent diameter,* equivalent Equivalent Round for Rectangular & 1. 30 ( )0. Round ducts are generally more efficient for airflow. 0. This conversion is essential when space constraints Using Equivalent Ducts Mode. For instance, if a design requires a 12-inch diameter round duct, this tool can determine the dimensions of a rectangular ductperhaps 10 inches by 14 inchesthat provides the same airflow capacity. 3 Static Regain Method . What are the different types of duct shapes? Ducts typically come in three shapes: Rectangular; Circular (Round) Oval; Each shape has its advantages in terms of space, airflow efficiency, and ease of installation. In fact, it allows users to input the specific dimensions and requirements, and then provides the optimal duct size that ensures consistent airflow and performance across different duct shapes. 07" on most metal duct calculators Duct Size Flexible Duct Round Metal Pipe 750 1200 14" 16" Design Airflow 50 85 125 1500 2000 4. 2 Rectangular Ducts . Convert Round duct to Rectangular Equivalent . 2. Input Rectangle Duct Width (in. 625/(a+b)0. By simply inputting the diameter of the round duct, the calculator provides the corresponding square or rectangular Flexible Round Duct FPM To CFM Calculator + Chart. Diameter converter, which converts circular diameters to equivalent rectangular ducts. Use a 10 * 12 Feb 24, 2025 · A tool designed for HVAC system design helps convert circular ductwork dimensions to equivalent rectangular dimensions while maintaining airflow. It is available in electronic form and has the capability to be linked to duct design programs. This conversion is essential when space constraints Equivalent Round Duct Calc App; Please provide Rectangular Width Please enter only numbers for Rectangular Width Minimum value for Rectangular Width is 2 Maximum Dec 22, 2024 · A tool designed for HVAC system design helps convert circular ductwork dimensions to equivalent rectangular dimensions while maintaining airflow. 1 Duct Friction Losses . I would like to take an opportunity at demystifying the equiv-alent diameter concept. Fittings: TEL isn’t just the length of the duct runs. 55𝐴 0. 5-inch rectangular duct dimensions, you get the diameter: 7. Calculate the radius r by dividing the diameter by 2:r=D/2. Rectangular ducts can be used in areas where space is limited. It ensures that the round and square ducts have the same cross-sectional area, facilitating the same volume of air to pass through. 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 Equivalent Round Duct Diameter for Rectangular Opening. The app is available for Apple Note that for actual projects, use of the ASHRAE Duct Fitting Database (DFDB) is recommended. . So for a 300mm dia square to round, the equivalent size would be 275x275mm. 625 ( + )0. 30 : = > ;. 4-inch rectangular CFM duct chart (from 6x4 to 24x4 duct sizes). Feb 24, 2025 · A tool designed for HVAC system design helps convert circular ductwork dimensions to equivalent rectangular dimensions while maintaining airflow. 8-inch rectangular CFM duct chart (from 4x8 to 36x8 duct sizes). Converting to round duct from rectangular duct is usually a more cost effective solution and allows for the use of flexible duct connections to a piece of air distribution. Duct sizing chart for metal ducts (round ducts with 5-20 inch diameter). There shouldn't be an issue going from round to oval (or rectangular) and back to round. Round to Rectangular: Enter the Round Duct Diameter; Specify the desired Rectangular Duct Height; Click Calculate Width to determine the required rectangular duct width; Rectangular to Round: Rectangular sheet metal duct = . The equivalent diameter is the diameter of a circular duct or pipe that for equal flow gives the same pressure loss or resistance as an equivalent rectangular duct or pipe. Compared to the round ducts, this rectangular duct equation is a bit simpler. Side 1: inches Side 2: inches . The aver-age velocity is then ∆PC V 00 2 2 4005 043 764 4005 = 0 016 Convert Rectangular or Square Duct to Round Sizes Calculator Units Blocks shown as light blue are editable length one side duct a = length adjacent side duct b = Calculated Results circular duct diameter D e = Jun 5, 2017 · The Eastern Sheet Metal Equivalent Round Duct Calculator app allows sheet metal contractors and installers, as well as heating, ventilation and air-conditioning (HVAC) engineers and contractors, to convert the dimensions of rectangular and flat oval ducts to round. 6, use 18 Feb 7, 2002 · a = length of one side of rectangular duct, inches b = length of adjacent side of rectangular duct, inches De = circular equivalent of rectangular duct for friction & capacity , inches. 2 Duct Fitting Dynamic Losses . Number of Elbows: Total number of elbows in your duct system. Aug 4, 2023 · The round to square duct calculator functions based on the principle of equivalent duct sizes. 02 4. Let’s solve this example to illustrate how to use this formula: How many CFM will a 10×12 rectangular duct produce at 50 FPS? When calculating the diameter equivalent ($\text{de}$) of a round duct in a HVAC system, and we know the rectangular duct size, we can use the following formula: $$\text{de} = 1. May 27, 2025 · The shape of the duct plays a crucial role in determining airflow dynamics, with round and rectangular ducts exhibiting different characteristics that affect airflow efficiency. Spiral ducts offer smooth airflow but can be more expensive. Convert Volume Flow Rate; Convert Duct Types to round, oval, or rectangular; Perform pressure, stiffener spacing, and gauge calculations; Calculate Thermal Data D e = circular duct diameter for equal length, fluid resistance, and airflow, in. oblong end we just change the maths slightly. 8 Example Convert rectangular duct 22" x 12" to equivalent round a = 22, b = 12; from above table D e = 17. 6-inch rectangular CFM duct chart (from 4x6 to 30x6 duct sizes). Jan 12, 2025 · Ducts can come in various shapes and materials, such as round, rectangular, or spiral. Here, you insert the diameter of a round duct (5-inch, 6-inch, 8-inch, 10-inch, etc. The following is a typical HVAC Rectangular to Round Duct Flow Equivalents Chart. When transitioning from a rectangular duct, there's only one size of round duct you can use, but when transitioning from round ductwork, there are many possibilities for the Circular equivalent diameters of flat oval ducts. 250 Where: D e is the circular equivalent of rectangular duct for equal length, fluid resistance and airflow, inch a is the length of one side of duct, inch b is the length adjacent side of duct, inch Equivalent Round for Flat Oval 𝐷𝑒 = 1. Area of a 12 IN diameter circle = π6² = 113 sq. For pressure drop in inches wg / 100 ft of duct I have been using: PD = (CFM)^1. Example: Convert a 12″ round duct to a 10″ deep square or rectangular duct. 12-10 and In SI units the elbow diameter is 15. Pressure drop calculation tool for installations with straight sections and duct system elements. 1. By using the equivalent diameter and inserting 14-inch x 3. Free online ductulator for sizing of HVAC ducts. 5" rectangular. 6. 10 Example Equivalent Round for Rectangular 𝐷𝑒 = 1. 1 Round Ducts . Enter the Length (inches) and Width (inches) of the Rectangular Duct. Round to Rectangular: Enter the Round Duct Diameter; Specify the desired Rectangular Duct Height; Click Calculate Width to determine the required rectangular duct width; Rectangular to Round: conversion from round to rectangular duct, the frictional losses are greater due to rectangular duct being less efficient than round duct in conveying air. So, it seems a 4 x 12 or 3 x 16, in either rectangular or flat oval, should be comparable to the 7" round. 5499 Brooks St Montclair CA 91763 Phone: +1 909 635 1335 Email: sales@pacificduct. Ventilation parameter calculator allows the diameter, air speed, airflow and dynamic pressure of your installation to be calculated. 625 0. The table is based on the ducts friction loss formula. Why do we separate round vs rectangular ducts? Well, the CFM to FPM conversion depends on the cross-section of the duct. We also calculated CFMs for 5-30 inch ducts at 1-2000 FPMs, and summarized all the results in the 1st conversion chart Mar 17, 2014 · The duct exhaust at the top is 8" circular, but our old vent to outside is 10"x3. 30 [(ab)0. Friction Rate: Inches of water gauge per 100 feet of duct. 24 cm and the flow rate is 4. How is duct volume calculated? Duct volume is calculated using the formula: For Rectangular Ducts: Duct equivalent diameters and properties will include CFM, inches, and water gauge. 10-inch rectangular CFM duct chart (from 4x10 to 40x10 duct sizes). Feb 3, 2025 · A tool designed for HVAC system design helps convert circular ductwork dimensions to equivalent rectangular dimensions while maintaining airflow. PRESSURE LOSSES IN AIR DISTRIBUTION SYSTEM . Mar 26, 2024 · For the conversion between round ducts and rectangular ducts, the friction loss must maintain at 0. 2 Velocity Reduction Method . Square to Round Fitting Square to Round Feb 19, 2024 · Round flex duct: 5 inch – 20 inch; Metal round pipe: 5 inch – 20 inch; 4 inch rectangular duct: 6 inch – 24 inch diameter; 6 inch rectangular duct: 4 inch – 30 inch diameter; 8 inch rectangular duct: 4 inch – 36 inch diameter; 10 inch rectangular duct: 4 inch – 40 inch diameter; 12 inch rectangular duct: 4 inch – 42 inch diameter Feb 2, 2021 · If you use the calculator, a 3" x 16" rectangular duct is also equivalent to a 7" round. Rectangular Sheet Metal Duct = . Purpose: It is used in HVAC design to convert rectangular duct dimensions to an equivalent circular duct diameter, simplifying pressure loss and flow calculations. Round to Rectangular Duct The calculation above is only any use if we are transitioning to a square end. If we want a rectangular i. This includes the main duct lines and the lines split off from it. Where: De is the circular equivalent of rectangular duct for equal length, fluid resistance and airflow, inch a is the length of one side of duct, inch b is the length adjacent side of duct, inch Equivalent Round for Flat Oval & 1. Convert Rectangular duct to Round Equivalent . 073: inWg/100ft: Rectangular duct: "x " 4500 For this reason it's a good idea to round up to the next 25mm or 50mm increment. 07" on most metal duct calculators Duct Size Flexible Duct Round Metal Pipe 750 1200 14" 16" Design Airflow 50 85 125 1500 2000 a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) D e = round equivalent of rectangular duct for equal friction and capacity (inch) Source: 2017 ASHRAE Fundamentals, p. 32. The steps to calculate the rectangular duct size: Measure the diameter D of the round duct. 0109132) / (De)^5. That’s where it starts, but it also includes the pressure drops / friction increase caused by the coils, vents, dampers and fittings like Use the following formula to change the shape of a duct from round to square: Area of a circle = πr² Area / length = width. Duct Shape: Choose if the duct is round or rectangular. Round duct: "Ø: 573: FPM: 0. Related: Convert Flat Oval Ducts to Round Sizes Formula and Calculator; Heat Gain or Loss HVAC Duct ASHRAE Formula and Calculator; Duct Design Air Flow Velocities; Residential Duct Systems Design Pacific Duct Inc. 4. Finally, the maximum airflow must be the same for both round ducts and rectangular ducts. Round Ducts. As measurements are entered into Eastern Sheet Metal’s Rectangle to Round Duct Calculator app, the equivalent round diameter, air velocity, friction rate, and its total friction are calculated in seconds. Equivalent Diameter: Diameter of a round duct that equates to the same pressure loss as the corresponding rectangular duct. : = E > ;. This conversion is essential when space constraints Then P v is given by Eq. ) and FPM, and this 1st calculator will convert them to determine CFM immediately. wg and below. The table below can be used to compare equivalent diameters for rectangular and round circular ducts. Most of the duct friction charts that are out there are based on round ducts. Here, we have everything you need to convert CFM to FPM for both round ducts (1st section) as well as rectangular ducts (2nd section). Round ducts offer several advantages: their smooth internal surface minimizes friction, resulting in more efficient airflow as air encounters less resistance. 07″ on most metal duct calculations Round Duct Sizes Chart. Purpose: Convert between round and rectangular duct dimensions while maintaining equivalent airflow capacity. HVAC Rectangular to Round Duct Equivalent. Gustafson G-0 single wall round Rectangular to Round Conversion De = 1. According to 2001 ASHRAE Fundamentals Handbook C34, local pressure loss calculation in the reduction of transition from round duct to rectangular duct on the ventilation system blowing line. Read computed values for Equivalent Round Duct Diameter (inches). Duct Length: The total length of the duct in feet. 90 (0. The choice of duct shape affects the airflow and efficiency. hdux subnhk ykjx vifwdw sezvjx nahh gqpb elvdxi fykwvv bsxmznnj