Tire inflation time calculator
Topping a 265/70R17 truck tire from 30 to 35 psi takes about 2 minutes with a compact inflator and about 45 seconds with a heavy-duty unit; filling the same tire from flat to 35 psi takes around 14 minutes with a compact unit.
Check pressure cold, before driving, for an accurate reading.
air needed (L) = tire volume x PSI rise / 14.7; minutes = air needed / delivered flow at tire pressureTire volume comes from the size on the sidewall. Delivered flow is roughly 40 to 50 percent of the rated free-air figure on the box, because output falls as pressure rises. Long runs heat small inflators; follow the maker's duty cycle and let it cool.
Inflators for this job
Prices from Amazon at the time of writing; they change often.
AstroAI L7 Tire Inflator Portable Air Compressor,150 PSI Cordless Bike Pump150 PSI / cordless$23.49Check price on Amazon
How long does it take to top up common tire sizes?
Time to raise one tire by 5 psi and to fill from flat to 35 psi, for the three inflator classes.
| Tire | Volume | +5 psi compact | +5 psi heavy | Flat to 35, compact |
|---|---|---|---|---|
| 185/65R15 | 30 L | 43 s | 16 s | 5.1 min |
| 215/60R16 | 40 L | 58 s | 21 s | 6.7 min |
| 225/65R17 | 51 L | 74 s | 27 s | 8.6 min |
| 235/60R18 | 53 L | 77 s | 28 s | 9.0 min |
| 245/45R19 | 43 L | 62 s | 23 s | 7.3 min |
| 265/70R17 | 81 L | 118 s | 44 s | 13.8 min |
| 275/65R18 | 83 L | 122 s | 45 s | 14.2 min |
| 285/70R17 | 96 L | 140 s | 51 s | 16.3 min |
Why is my inflator slower than the box says?
The rated flow on the box, in liters per minute or CFM, is measured with no back pressure. Against 30 psi in a tire, a small piston compressor delivers perhaps 40 to 50 percent of that. Heat also slows it: most compact units are rated for about 10 minutes of running before a cool-down.
Large truck tires are where the class matters. A 285/70R17 holds about twice the air of a 205/55R16, so a compact inflator that tops up a sedan in under a minute takes several minutes per tire on a pickup.
Frequently asked questions
How long does a portable tire inflator take to fill a tire?
Topping up a car tire by 5 psi takes about 40 to 90 seconds with a compact unit. Filling a flat passenger tire to 35 psi takes around 4 to 7 minutes; a large truck tire can take 12 to 15 minutes with a compact unit and about 5 with a heavy-duty compressor.
Can a portable inflator fill a completely flat tire?
Yes, if the tire is still seated on the rim, but it takes several minutes and may exceed a compact unit's duty cycle. If the bead has come off the rim, a portable inflator cannot reseat it. Find and plug the leak first, or fit the spare.
What is a good CFM for a tire inflator?
For cars, the 0.7 to 1.2 CFM class is fine for top-ups. For pickups and SUVs with large tires, or for airing back up after off-roading, look at 1.5 to 2.5 CFM heavy-duty units that clamp to the battery and have a long duty cycle.
Should I check tire pressure hot or cold?
Cold, before driving or after the car has sat for three hours. Driving warms the air and raises the reading by 2 to 4 psi, so a hot reading makes an underinflated tire look correct. The placard pressure on the door jamb is a cold pressure.