Pump-up time calculator
Enter your compressor's output (CFM), tank size, and target pressure to instantly calculate how long it will take to fill from empty — or from any starting pressure. Useful for sizing a new tank, diagnosing slow recovery, or confirming a compressor is performing to spec.
Small auto shop
60-gal tank, 5 HP / 14 CFM, 125 PSI
Spray & body work
80-gal tank, 7.5 HP / 21 CFM, 175 PSI
Rotary screw system
240-gal receiver, 25 HP / 100 CFM, 125 PSI
Portable / job site
6-gal pancake, 2 CFM, 150 PSI
T (min) = (V × (P₂ − P₁)) ÷ (14.7 × CFM_effective × 60)Where
V = tank volume in cubic inches, P₂ = target pressure (PSIA), P₁ = start pressure (PSIA), CFM_effective = rated CFM × efficiency − simultaneous draw, and 14.7 = atmospheric pressure (PSIA at sea level).
| Tank size | Pump-up time | vs. your tank |
|---|
What is pump-up time and why does it matter?
Pump-up time — also called recovery time — is the time it takes a compressor to fill a receiver tank from empty (or from cut-in pressure) to cut-out pressure. It's one of the most practical indicators of whether your compressor is properly sized for your application.
When pump-up time tells you something is wrong
If your compressor takes significantly longer than the calculated time above to pump up, it's a symptom of one of these problems:
| Symptom | Likely cause | Action |
|---|---|---|
| Takes 2–3× longer than calculated | Worn valves (piston) or worn airend (rotary screw) — actual CFM output has dropped | Have output tested; service or replace worn components |
| Never reaches cut-out pressure | Significant leak in system, failed check valve, or severely undersized compressor for the load | Leak test, check valve inspection, or size up compressor |
| Pumps up fast but drops quickly | Tank is properly sized but compressor can't keep up with peak demand — undersized CFM | Add a larger receiver tank or upgrade compressor CFM |
| Runs constantly, never unloads | Demand exceeds compressor output — system is starved for air | Add second compressor or upgrade to higher CFM unit |
How tank size affects recovery
A larger receiver tank acts as a buffer — it stores compressed air so the compressor doesn't have to run continuously to meet short bursts of demand. The tradeoff: a larger tank takes longer to pump up initially, but once charged it sustains peak demand for longer before the compressor needs to restart. For most applications, the right tank size is 4–6 gallons per CFM of compressor output.
Altitude correction
At higher elevations, atmospheric pressure is lower — air is less dense — so your compressor moves less mass per CFM and takes longer to build pressure. At 5,000 feet, expect roughly 15–20% longer pump-up times than at sea level. At 10,000 feet, add 30–40%. If you're in Denver or higher, factor this into your sizing.
Not sure if your system is sized right?
Our applications engineers review your pump-up data and tool requirements, and recommend the right compressor and tank combination for your application.