Tools · inflation time
How long will your tyre take?
Every published inflator time is measured on one tyre. Car and Driver used a 245/50R20 on a Hyundai Santa Cruz. If you drive a Miata or an F-150, that number is not your answer — so put your size in and get one.
Scale set by the slowest unit shown.
use it Car and Driver, Best Portable Tire Inflators of 2026, Tested, 17 February 2026. One tyre on one vehicle: a 245/50R20 on a 2023 Hyundai Santa Cruz, let down to 10 psi on a handheld gauge, then each inflator timed to 30 psi and again to 45 psi. Noise averaged in dBA and sone over 15 seconds of running. Each unit's own gauge was checked against the handheld one before and after.
What the arithmetic is
A tyre's air space is the ring between the rim and the tread. From a size, the sidewall height is width × aspect / 100, the outer diameter is rim + two sidewalls, and the air space is proportional to (outer² − rim²) × width.
That expression is proportional to the volume, not equal to it: a real tyre is not a rectangular ring, and the fill factor that corrects for its actual shape is not published anywhere we could find. It does not matter here, because the fill factor cancels when you divide one tyre by another. This tool only ever computes a ratio, which is why it can be honest about a number it cannot know.
The time then scales with the ratio, and with the pressure span you asked for against the span that was measured.
Three things this cannot tell you
- It assumes the pump's output does not change. It does. On the measured figures, every unit but the Milwaukee took noticeably longer per psi in the 30–45 band than in the 10–30 band — up to 1.67 times longer. Above about 45 psi these estimates will read optimistic, and they will read most optimistic for the smallest pumps.
- It assumes your compressor is the one that was measured. The same model in a hot boot after two years is not the unit that came out of a box in a Michigan garage.
- It ignores temperature. Air warms as it is compressed and the gauge reads high while it does; the pressure you set on a cold morning is not the pressure you have twenty minutes later.
Treat the answer as the right order of magnitude, which is what you actually need when deciding whether to keep a 1.1 lb inflator or an 8.7 lb one in the boot.