Calculate compressor tank volume, flow rate, or time from any 2 values with gallons/liters, CFM/L/min, and minutes or hours, and view calculation steps.
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Compressor Time Formula
The compressor time calculator uses the relationship between tank volume, flow rate, and time. The calculation assumes the volume and flow rate are expressed on the same basis, then converts units as needed.
- t = time
- V = tank volume
- Q = flow rate
To calculate the missing value, the same formula can be rearranged:
- V = tank volume, in gallons or liters
- Q = flow rate, in CFM or L/min
- t = time, in minutes or hours
The calculator converts all inputs to base units before calculating: liters for volume, liters per minute for flow rate, and minutes for time.
- Calculate time: enter tank volume and flow rate. The calculator divides volume by flow rate.
- Calculate tank volume: enter flow rate and time. The calculator multiplies flow rate by time.
- Calculate flow rate: enter tank volume and time. The calculator divides volume by time.
Common Compressor Unit Conversions
These are the unit conversions used by the calculator.
| Measurement | Conversion |
|---|---|
| Gallons to liters | 1 gallon = 3.78541 liters |
| Liters to gallons | 1 liter = 0.264172 gallons |
| CFM to L/min | 1 CFM = 28.3168 L/min |
| Hours to minutes | 1 hour = 60 minutes |
Typical Air Compressor Tank Sizes
| Tank Size | Common Use |
|---|---|
| 1 to 6 gallons | Small nailers, inflating tires, light-duty portable use |
| 8 to 20 gallons | Garage tools, intermittent air tool use |
| 30 to 60 gallons | Shop compressors, longer tool runtime |
| 80 gallons or more | Larger stationary systems and higher air demand |
Example Compressor Time Calculations
Example 1: Calculate time from tank volume and flow rate
You have a 20 gallon tank and a flow rate of 5 CFM.
Convert the tank volume to cubic feet:
Convert the flow rate to liters per minute:
Now divide volume by flow rate:
The time is about 0.5347 minutes, or about 32.1 seconds.
Example 2: Calculate flow rate from tank volume and time
You have a 50 liter tank and it takes 4 minutes.
The flow rate is 12.5 L/min. If you select CFM, that is:
FAQ
Does this calculator account for pressure?
No. This calculator uses only tank volume, flow rate, and time. It does not account for starting pressure, final pressure, temperature, compressor efficiency, or pressure drop. For a real compressor fill-time calculation from one PSI level to another, pressure must also be included.
Why does CFM need to be converted?
CFM is cubic feet per minute, while the calculator uses liters per minute internally. Since tank volume may be entered in gallons or liters, the calculator converts all values to consistent base units before solving the formula.
What should I enter if I want to calculate the missing value?
Enter exactly two values and leave the third field blank. For example, to calculate time, enter tank volume and flow rate, then leave the time field empty.
