Calculate air usage, flow rate, or operating time from any 2 inputs with cfm, m³/min, L/s, minutes, hours, and cubic feet or liters.
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Air Usage Formula
The air usage calculation is based on flow rate multiplied by operating time. The calculator converts the entered units to base units first, using cubic feet per minute for flow rate, minutes for time, and cubic feet for total air usage.
AU = Q * t
Q = AU / t
t = AU / Q
- AU = total air usage, usually in cubic feet, cubic meters, or liters
- Q = flow rate, usually in cfm, m³/min, or L/s
- t = operating time, usually in minutes or hours
If you leave Air Usage blank, the calculator multiplies flow rate by operating time. If you leave Flow Rate blank, it divides total air usage by operating time. If you leave Operating Time blank, it divides total air usage by flow rate.
Air Flow and Volume Unit Conversions
These conversions are commonly used when comparing air flow rates and total air volume.
| Flow rate unit | Equivalent | Use in calculation |
|---|---|---|
| 1 cfm | 1 cubic foot per minute | Base flow rate unit |
| 1 m³/min | 35.3147 cfm | Metric flow converted to cfm |
| 1 L/s | 2.11888 cfm | Liter-per-second flow converted to cfm |
| Volume unit | Equivalent | Use in calculation |
|---|---|---|
| 1 cubic foot | 1 cf | Base air usage unit |
| 1 cubic meter | 35.3147 cf | Metric volume converted to cubic feet |
| 1 liter | 0.0353147 cf | Liter volume converted to cubic feet |
Examples
Example 1: Calculate total air usage
You have a tool that uses 12 cfm and it runs for 30 minutes.
AU = 12 * 30 = 360 cf
The total air usage is 360 cubic feet.
Example 2: Calculate operating time
You have 900 cubic feet of air usage and a flow rate of 15 cfm.
t = 900 / 15 = 60 minutes
The operating time is 60 minutes, or 1 hour.
FAQs
What does air usage mean?
Air usage is the total volume of air consumed over a period of time. For example, a device using 10 cfm for 20 minutes uses 200 cubic feet of air.
What is the difference between cfm and cubic feet?
cfm is a flow rate. It means cubic feet per minute. Cubic feet is a total volume. Flow rate tells you how fast air is being used, while total volume tells you how much air was used overall.
Why does operating time need to match the flow rate unit?
Flow rate includes a time unit. A rate in cfm means cubic feet per minute, so the time must be in minutes before multiplying. If you enter hours, the calculator converts hours to minutes before applying the formula.
