How to Check and Fill Tire Pressure
Low tires wear out faster, waste gas and handle worse. Checking takes five minutes with an inexpensive tire gauge. The trick is using the right number, and checking at the right time.
Use the number on your door jamb, not the tire
Open the driver's door and look at the edge of the door or the frame for the Tire and Loading Information label. That shows the cold pressure your car's maker recommends, often different for front and rear. The number molded into the tire's sidewall is the maximum the tire can hold, not what you should fill it to.
October is a good time to check: as nights get colder, pressure drops about 1 PSI for every 10°F, and that's when the warning light starts coming on.
HOWCheck and fill your tires
Do them in order. Repeat for all four tires, plus the spare.
- Look on the driver's door edge or door frame for the label. If it isn't there, it's in your owner's manual (some cars put it inside the glove box or fuel door).
- Note the front, rear and spare numbers separately. Many cars use the same number front and rear, but not all.
- Ignore the “Max press” on the tire sidewall. NHTSA says to use what the vehicle manufacturer lists, not what's on the tire.
- “Cold” means the car hasn't been driven for at least three hours. First thing in the morning is ideal.
- Driving warms the tires and temporarily raises the pressure, so a reading right after a drive looks higher than it really is.
- If you have to fill up at a gas station after driving, it's fine to add air, but recheck later when the tires are cold.
- Unscrew the small cap on the tire's valve stem and put it in your pocket.
- Press the gauge straight and firmly onto the valve. A short hiss is normal; a long hiss means it isn't seated, so press harder.
- Read the number. Pencil gauges push out a stick; dial and digital gauges show it on the face.
- Write it down, and do the other tires.
- At an air machine or with a portable inflator, press the hose onto the valve and add air in short bursts.
- Many machines let you set the target PSI and beep when it's reached. Otherwise, check with your gauge after each burst.
- Went over? Press the small pin in the center of the valve with the back of your gauge or a fingernail to let air out, a second at a time.
- Check each tire one more time with your gauge, then screw the valve caps back on. They keep dirt and moisture out of the valve.
- Check the spare too. Temporary spares often need a much higher pressure, commonly around 60 PSI; the number is on the spare or the door label.
- Make it a habit: NHTSA recommends checking all tires, including the spare, at least once a month and before long trips.
- Light stays on: at least one tire is significantly underinflated. Check and fill all tires as soon as possible.
- Comes on on a cold morning, then goes off after driving: the cold dropped the pressure and driving warmed it back up. Your tires are still low; fill them to the door number when cold.
- Flashes for about a minute, then stays on: that's a fault in the monitoring system itself. Have the dealer or a tire shop check it.
- After filling, some cars clear the light on their own after a few minutes of driving; others need a reset button or menu. Your owner's manual explains which.
If a tire loses air within days, or the warning light won't go off after all tires are at the right pressure, have a tire shop look for a leak or a faulty sensor.
TRYCold weather calculator
Filling up in a warm garage before a freezing night? See what your tires will read once the temperature changes. It uses the gas law on absolute pressure, which lands very close to the 1 PSI per 10°F rule of thumb.
TRYPSI, bar and kPa converter
Some cars, gauges and air machines show bar or kPa instead of PSI. Type a number in any box.
FAQCommon questions
Should I fill to the number on the tire?
No. The sidewall number is the tire's maximum. Fill to the cold pressure on your car's door-jamb label or in the owner's manual.
Should I add extra air in winter?
Fill to the recommended number when the tires are cold at the outdoor temperature. If you fill in a heated garage, the pressure will drop when you go out into the cold, so check again outside or use the calculator above.
Is it OK to check right after driving?
The reading will be high. If a tire looks low even when warm, add air anyway, then recheck when it's cold. Never let air out of hot tires to reach the cold number.
My car has a tire pressure light. Do I still need a gauge?
Yes. NHTSA notes the warning only comes on when a tire is significantly underinflated, so it isn't a substitute for a monthly check with a gauge.
Nitrogen or regular air?
Either is fine. Regular air is already mostly nitrogen. What matters is checking the pressure regularly.