Enter the tank volume, compressor flow rate (as SCFM/FAD), initial tank pressure, and target tank pressure into the Air Compressor Fill Time Calculator. The calculator estimates the time required to raise the tank pressure from the initial value to the target value using an ideal-gas/isothermal approximation.

Air Compressor Fill Time Calculator

Enter any 4 values to calculate the missing variable (flow rate should be SCFM/FAD).

Air Compressor Fill Time Formula

The following example problem outlines the steps and information needed to estimate air compressor tank fill time.

FT=\frac{CV\,(P_2-P_1)}{P_{atm}\,FR}

Variables:

  • FT is the fill time (minutes)
  • CV is the tank volume (ft³)
  • FR is the compressor flow rate as free air (SCFM, i.e., ft³/min at standard conditions)
  • P1 is the initial tank pressure (gauge)
  • P2 is the target tank pressure (gauge)
  • Patm is atmospheric pressure (≈ 14.7 psi, 101.3 kPa, or 1.013 bar)

To estimate the air compressor tank fill time, multiply the tank volume by the pressure rise (P2 − P1), divide by atmospheric pressure to get the equivalent “free-air” volume, then divide by the compressor’s free-air flow rate (SCFM). Real-world fill time can vary because compressor flow typically changes with pressure and the air heats up during compression.

How to Calculate Air Compressor Fill Time?

The following steps outline how to estimate the Air Compressor Fill Time.

  1. First, determine the tank volume (ft³).
  2. Next, determine the compressor free-air flow rate (SCFM).
  3. Next, determine the initial tank pressure (P1) and target tank pressure (P2) as gauge pressures.
  4. Next, gather the formula from above: FT = CV × (P2 − P1) / (Patm × FR).
  5. Finally, calculate the Air Compressor Fill Time.
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

tank volume (ft³) = 8.0 (≈ 60 US gal)

compressor flow rate (SCFM) = 10

initial tank pressure, P1 (psig) = 0

target tank pressure, P2 (psig) = 125

FT = [CV × (P2 − P1)] / (Patm × FR) = [8.0 × (125 − 0)] / (14.7 × 10) ≈ 6.80 minutes