Calculate CFM, FPM, or area from air velocity and cross-sectional area, including round or rectangular duct dimensions in common units.
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| FPM to CFM | CFM to FPM |
|---|---|
| 300 fpm = 600 cfm | 100 cfm = 50 fpm |
| 400 fpm = 800 cfm | 150 cfm = 75 fpm |
| 500 fpm = 1000 cfm | 200 cfm = 100 fpm |
| 600 fpm = 1200 cfm | 250 cfm = 125 fpm |
| 700 fpm = 1400 cfm | 300 cfm = 150 fpm |
| 800 fpm = 1600 cfm | 400 cfm = 200 fpm |
| 900 fpm = 1800 cfm | 500 cfm = 250 fpm |
| 1000 fpm = 2000 cfm | 600 cfm = 300 fpm |
| 1200 fpm = 2400 cfm | 800 cfm = 400 fpm |
| 1500 fpm = 3000 cfm | 1000 cfm = 500 fpm |
| Formulas: CFM = FPM × Area and FPM = CFM ÷ Area. Table assumes Area = 2 sq ft. | |
| FPM to CFM | CFM to FPM |
|---|---|
| 400 fpm = 140 cfm | 100 cfm = 286 fpm |
| 500 fpm = 175 cfm | 150 cfm = 430 fpm |
| 600 fpm = 209 cfm | 200 cfm = 573 fpm |
| 700 fpm = 244 cfm | 250 cfm = 716 fpm |
| 800 fpm = 279 cfm | 300 cfm = 859 fpm |
| 900 fpm = 314 cfm | 350 cfm = 1003 fpm |
| 1000 fpm = 349 cfm | 400 cfm = 1146 fpm |
| 1200 fpm = 419 cfm | 500 cfm = 1432 fpm |
| 1500 fpm = 524 cfm | 600 cfm = 1719 fpm |
| 1800 fpm = 628 cfm | 800 cfm = 2292 fpm |
| Formulas: CFM = FPM × Area and FPM = CFM ÷ Area. For 8 in round duct, Area = π × (8 in)² ÷ (4 × 144) ≈ 0.3491 sq ft. Values rounded to nearest whole. | |
FPM to CFM Formula
The following formula is used to calculate CFM from FPM.
CFM = FPM * A
- Where CFM is the cubic feet per minute
- FPM is the feet per minute
- A is the area (ft^2)
To calculate CFM from FPM, multiply the FPM by the area in square feet.
What is the difference between FPM and CFM?
FPM stands for feet per minute and is a unit of measure that describes length per unit time.
CFM stands for cubic feet per minute and is a unit of measure that describes volume per unit time.
To convert between the two, the length in FPM must be multiplied by the area to get volume.
How to calculate CFM from FPM?
Example Problem:
The following example outlines how to calculate CFM from FPM.
First, determine the total feet per minute. In this example, the feet per minute are measured to be 25 fpm.
Next, determine the area. For this problem, the area is measured to be 20 ft^2.
Finally, calculate the CFM using the formula above:
CFM = FPM * A
CFM = 25 * 20
CFM = 500
