Tire Pressure Calculator
Pressure, temperature, and load
Estimated pressure result
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Quick answer: temperature changes the reading, not the placard target
For normal passenger-vehicle use, set cold tires to the vehicle manufacturer’s placard pressure at the current outdoor temperature. If the air cools without leaking, gauge pressure falls; if it warms, pressure rises. The calculator predicts that change with absolute temperature and absolute pressure.
The model assumes a sealed tire, nearly constant internal volume, and sea-level atmospheric pressure. Real readings also vary with gauge accuracy, altitude, tire flex, solar heating, moisture, small leaks, and the difference between ambient air and the air inside the tire.
A predicted lower reading is not permission to run below the placard. Check tires cold and add air to the placard value. Pressure gained during normal driving should not be bled off.
How the optional load estimate works
When both loads are entered, the tool calculates a simple screening value:
It never screens below the placard value. This proportional relationship is deliberately easy to audit, but tire load capacity is not governed by one universal linear formula. Tire construction, size, load range, single/dual use, speed, wheel rating, axle distribution, and the applicable TRA, ETRTO, or manufacturer table can change the required pressure.
Use it as a table-check prompt, not an inflation instruction. For RVs, trailers, towing, commercial vehicles, replacement tire sizes, or materially changed axle loads, weigh each axle or axle end as directed and use the exact tire manufacturer’s current load/inflation table. Keep equal pressures across an axle unless the vehicle maker specifies otherwise.
How to check and adjust tire pressure safely
- Find the correct cold target. Read the driver-door tire label and owner’s manual. Front and rear pressures may differ.
- Wait for cold tires. NHTSA defines cold as not driven for at least three hours. Park out of direct sun where practical.
- Measure every tire. Use an accurate gauge, including on the spare if applicable. A visual check is not enough.
- Adjust to the specified cold pressure. Do not substitute the maximum pressure marked on the tire sidewall for the vehicle recommendation.
- For changed load or tire size, verify the table. Confirm vehicle payload, axle ratings, wheel limits, and the exact tire’s load/inflation data.
- Recheck after conditions stabilize. Investigate repeated loss, damage, bulges, cuts, unusual wear, or a persistent TPMS warning with a qualified tire professional.
Temperature and load examples
| Scenario | Inputs | Estimate | What to do |
|---|---|---|---|
| Cold weather | 35 psi at 68°F, then 32°F | About 31.6 psi if sealed | Check cold and restore the vehicle’s placard pressure. |
| Warm weather | 35 psi at 68°F, then 95°F | About 37.5 psi if sealed | Do not bleed merely because temperature raised the reading; recheck cold. |
| Load screening | 35 psi baseline; 1,000 lb to 1,100 lb per tire | 38.5 psi proportional screening value | Check the exact tire table, vehicle/wheel limits, and axle ratings before changing pressure. |
Tire pressure FAQs
How much does tire pressure change with temperature?
The familiar rule is roughly 1 psi per 10–12°F, but it is only a shortcut. The precise ideal-gas estimate depends on the starting pressure and both absolute temperatures. The calculator uses that fuller relationship.
Should I use the PSI on the tire sidewall?
No. For normal operation, start with the vehicle manufacturer’s cold pressure on the driver-door placard or in the owner’s manual. The sidewall marking describes a tire rating or limit, not the vehicle’s ordinary target.
Should I release air from a warm tire?
Normally no. Driving warms tires and raises pressure. Wait until the vehicle has been parked for at least three hours, then check against the cold placard pressure. If a warm tire appears low, NHTSA advises adding enough air for safety and rechecking cold later.
Can vehicle weight alone determine the correct PSI?
No. Weight is only one input. The exact tire size and construction, load range, single or dual use, axle distribution, wheel limit, speed, and manufacturer load/inflation table matter. The load-ratio result here is only a screening estimate.
Does the placard pressure already allow for passengers and cargo?
For an ordinary passenger vehicle using its approved tires within its rated load, the manufacturer’s placard specifies the cold pressure for the vehicle’s approved loading conditions. Do not lower pressure simply because the vehicle is lightly loaded, and never exceed vehicle payload or axle ratings.
Why does TPMS sometimes turn on during a cold morning?
A temperature drop can lower gauge pressure enough to cross the warning threshold. Check every tire with a gauge and restore the manufacturer’s cold placard pressure rather than waiting for driving heat to turn the light off.
Can I use this for RV, trailer, or commercial tires?
Use the temperature prediction only as an estimate. For pressure selection, obtain actual axle or axle-end weights and use the exact tire maker’s current table, including single/dual configuration and wheel limits. A tire professional should review uncertain applications.
Are my pressure and load inputs tracked?
No. The calculation runs locally in your browser. This tool does not upload, store, or attach input values to analytics events.
Limits and safety disclaimer
- The temperature model is an ideal-gas estimate. It does not diagnose a leak, puncture, valve problem, TPMS fault, overheated tire, or structural damage.
- The load screen uses a proportional ratio, not a tire-specific TRA, ETRTO, or manufacturer table. Do not use it to certify capacity or justify overload.
- Never exceed the lowest applicable tire, wheel, vehicle, axle, or manufacturer limit. Do not exceed vehicle payload or gross/axle weight ratings.
- Replacement sizes, LT tires on passenger vehicles, towing, dual configurations, off-road use, high speeds, and motorsport require application-specific guidance.
- Pressure recommendations can differ front to rear. Run this calculator separately for each axle and preserve the vehicle maker’s specified axle relationship.
Safety disclaimer: This calculator provides an educational estimate, not a fitment approval, inspection, or professional inflation recommendation. When sources conflict, follow the vehicle manufacturer, current tire-specific data, wheel limits, and a qualified tire professional.
Methodology and sources
Last reviewed: July 31, 2026. Temperature prediction applies the ideal-gas relationship to absolute pressure and absolute temperature. Safety guidance and table-use limits were checked against the following primary industry and government material:
- NHTSA TireWise: cold pressure, placard use, warm-tire guidance, and TPMS basics
- NHTSA winter driving tips: temperature-related pressure loss and placard pressure
- Michelin: RV tire load/inflation tables and axle-end weighing guidance
- U.S. Tire Manufacturers Association: load/inflation tables and manufacturer-table caveat (PDF)