# How do you calculate CFM for duct size?

## How do you calculate CFM for duct size?

To calculate CFM, you need to know the size of your heating or cooling unit in tons. Multiply this number by 400, which is the average output of an HVAC unit. Then divide by the total square footage of your home. This will give you the multiplier for all your rooms’ CFM.

### How many CFM does a 4 round duct have?

Reviewing the chart, a 4” pipe will convey 395 CFM at 4500 FPM. This means that a 4” pick-up on a machine will use 395 CFM from the filtering system; or, if you know that a machine will require approximately 400 CFM to remove the waste, you should use a 4” pipe for that purpose.

What size duct do I need for 800 cfm?

Equivalent diameter for rectangular and circular ducts – air flows between 100 – 50000 cfm

Air flow – q – (Cubic Feet per Minute, cfm) (m3/s) Rectangular Duct Sizes (inches) (mm) x (mm)
800 (0.36) 8 x 15 10 x 12
1000 (0.45) 10 x 14 12 x 12
1300 (0.59) 12 x 14
1400 (0.63) 12 x 15

How many CFM can a 12 inch duct handle?

CFM Sizing Chart For Metal Round Ducts (50-2,000 CFM)

Duct Size (Inches) Metal Duct Airflow (CFM)
8 inches 180 CFM
9 inches 240 CFM
10 inches 325 CFM
12 inches 525 CFM

## How many CFM is a 3 ton unit?

1200 CFM
A 3-ton heat pump has approximately 1200 CFM of air flow.

### How many CFM is a 7 round duct?

CFM Sizing Chart For Flex Round Ducts (50-1,700 CFM)

Duct Size (Inches) Flex Duct Airflow (CFM)
6 inches 75 CFM
7 inches 110 CFM
8 inches 160 CFM
9 inches 225 CFM

How many CFM is a 8 round duct?

CFM Sizing Chart For Metal Round Ducts (50-2,000 CFM)

Duct Size (Inches) Metal Duct Airflow (CFM)
6 inches 85 CFM
7 inches 125 CFM
8 inches 180 CFM
9 inches 240 CFM

How do you calculate the CFM of a duct?

Measure the length and width of the room where the flex duct will be supplying the air. Multiply the length and width together to get the square footage of the room. For example, a 10-by-10 room will be 100 square feet. Figure out the amount of CFM that is required for the room. Properly ventilated homes use 1 CFM per square foot of space.

## What is the CFM of duct?

CFM stands for cubic feet per minute. If a room is supplied with 100 CFM, that means there will be 100 cubic feet of air dispensed into that room each minute. Duct runs that are too small will not supply enough air and will have increased velocity, which leads to noise. Duct runs that are too big will have low velocity.

### What is duct size?

Rectangular or square ducting comes in standard sizes ranging from 3-by-7 inches to 35-by-40 inches. Sizing is based on airflow needs per cubic foot per minute, as well as velocity.