Car Tire Pressure Calculator

Cold tire plan

Front {{ axles[0] ? axles[0].targetPsiDisplay : '—' }} / Rear {{ axles[1] ? axles[1].targetPsiDisplay : '—' }}

Check your inputs

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Vehicle class:

Pick the nearest class: compact, sedan, wagon/CUV, SUV, pickup, or EV/performance.

Baseline:

Choose Door placard when you have front and rear cold psi from the vehicle sticker.

Door placard cold pressures:

Enter sticker values such as Front 33 psi and Rear 35 psi; use cold-pressure numbers only.

Front psi Rear psi

Weight unit:

Use kg or lb; changing units converts existing weight entries.

Curb weight:

Enter curb weight with fluids, not gross vehicle weight; example 1500 kg.

Passengers:

Include the driver; allowed range is 1 to 8 people.

people

Average passenger weight:

Enter the trip average per person, for example 75 kg or 165 lb.

Cargo weight:

Enter luggage, tools, roof-box contents, and other load beyond passengers.

Front tire width:

Enter the first tire-size number, e.g. 235 from 235/45 R18.

Rear tire width:

Match the rear tire sidewall size; leave equal to front for square setups.

Front axle share:

Set 45-65%; typical FWD is 55-60%, balanced RWD often 50-55%.

{{ front_share_percent }}%

Surface:

Select highway, city/mixed, rough roads, or winter/cold conditions.

Priority:

Use Balanced unless you deliberately want softer ride or firmer support.

Tire setup:

Choose the tire type fitted now: all-season SL, summer, winter, or XL.

Temperature unit:

Choose Fahrenheit or Celsius before entering today and forecast values.

Current check temperature:

Use the cold-soak temperature at the reading, e.g. 68 F or 20 C.

Forecast next cold temperature:

Enter the next morning or parked-cold temperature, e.g. 40 F or 5 C.

Current cold readings:

Enter front/rear cold psi if measured; leave blank to compare targets only.

Front psi Rear psi

Front tire max:

Set psi only when the front tire maximum should be below the computed ceiling.

psi

Rear tire max:

Set psi only when the rear tire maximum should limit the recommendation.

psi

Axle	Load	Baseline	Target	Adjust now	Forecast	Safe
Recommendation {{ recommendationHeadline }}	{{ systemWeightDisplay }} {{ classLabel }}	{{ baselineBadge }}	{{ setupLabel }}	{{ summaryNote }}	{{ forecastTemperatureDisplay }}	{{ terrainLabel }}
Before you drive Check {{ index + 1 }}	{{ systemWeightDisplay }}	{{ baselineBadge }}	—	{{ item }}	{{ forecastTemperatureDisplay }}	{{ terrainLabel }}
{{ row.axle }} {{ row.note }}	{{ row.loadKgDisplay }} {{ row.loadLbDisplay }}	{{ row.basePsiDisplay }} {{ row.baselineDeltaDisplay }}	{{ row.targetPsiDisplay }} {{ row.bandPsiDisplay }}	{{ row.actionLabelDisplay }} {{ row.currentPsiDisplay }}	{{ row.forecastPsiDisplay }} {{ row.temperatureShiftDisplay }}	{{ row.safeRangeDisplay }} {{ row.tpmsFloorDisplay }}
Enter values to see a cold tire plan.

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Tire pressure is a cold measurement, not a random gauge reading taken whenever the car happens to stop. Vehicle makers publish recommended inflation values for tires that have cooled after sitting, because driving heat, sunlight, and garage temperature can raise pressure temporarily. A tire that looks correct after a highway trip may be several psi lower the next cold morning.

The vehicle placard and owner manual are the normal starting point for passenger cars. Those numbers account for the vehicle's axle loads, original tire size, suspension tuning, ride goals, and handling balance. The maximum pressure molded on the tire sidewall is different: it is a tire limit, not the daily pressure target for the vehicle.

Load and axle balance are the next questions. A front-heavy sedan, a loaded wagon, a pickup with cargo in the bed, and an electric vehicle with a heavy battery can need different front and rear support. Underinflation lets the tire flex more, which can build heat, waste energy, wear shoulders, and reduce control. Overinflation can make the ride harsher and reduce the tread area working on the road.

Temperature moves pressure even when no air leaks out. A common passenger-car rule of thumb is about 1 psi for each 10°F change in cold-soak air temperature. A tire set on a warm afternoon can look low after a cold front, and a tire inflated on a cold morning can read higher after the weather warms.

Any pressure estimate should stay below the tire sidewall maximum and within the vehicle maker's instructions. Modified tire sizes, towing, heavy cargo, track use, commercial service, visible tire damage, or repeated pressure loss call for the owner manual, tire load tables, and a qualified tire professional rather than a simple passenger-car estimate.

How to Use This Tool:

Use door-placard mode when you have the front and rear cold psi values. Use vehicle-class presets only as a temporary estimate when the label or manual is not available.

Choose Vehicle class, then set Baseline. Select Door placard when you know the vehicle's front and rear cold pressures.
Enter Door placard cold pressures when placard mode is selected. These values also set the placard-based tire pressure monitoring system floor used by the forecast warning.
Pick the Weight unit, then enter Curb weight, Passengers, Average passenger weight, and Cargo weight. Include the driver in the passenger count.
Enter the front and rear tire widths from the first number in the tire size, such as 235 from 235/45 R18, and set Front axle share to match the vehicle's load split.
Choose Surface, Priority, and Tire setup. These apply small pressure biases for rough roads, winter use, highway driving, comfort, efficiency, handling, summer tires, winter tires, or XL tires.
Set Current check temperature and Forecast next cold temperature. The forecast uses the cold-soak temperature change, not tire heat from driving.
Add Current cold readings when you want Add, Bleed, or On target instructions. Leave them blank when you only need target pressures.
Open Advanced only when a front or rear tire maximum should cap the safe window. Enter 0 to disable that override.
Correct any Check your inputs warning before using the pressure rows. Unrealistic tire widths, missing placard values, invalid temperatures, or an impossible tire-max clamp can hide results.

Interpreting Results:

Target is the modeled cold pressure for each axle after load, baseline, setup, surface, priority, width, and safe-window limits are applied. Treat it as a planning value to compare against the placard and the tire sidewall, not as permission to exceed the vehicle or tire limits.

Baseline shows the placard or vehicle-class pressure used before load and setup changes.
Adjust now compares the target with entered current cold readings. With no readings entered, the plan stays in target-only mode.
Forecast estimates where the pressure may land at the next cold-soak temperature if the current reading or target is left unchanged.
Safe shows the active working range. A target clipped by the safe minimum or maximum needs manual review.
Load Map shows how front and rear targets change as loaded vehicle weight changes around the current setup.
Seasonal Drift shows pressure movement across temperature changes, including the working range and the placard-based tire-pressure monitoring floor when placard mode is active.
Forecast near TPMS floor means a forecast value is close to 75% of placard pressure. Inspect for leaks, punctures, valve damage, rim damage, or sidewall damage before driving at speed.

Technical Details:

A cold tire-pressure estimate needs a baseline pressure, a loaded axle weight, and a safe window. Placard mode uses the front and rear cold pressures chosen for the specific vehicle. Preset mode uses the selected vehicle class, reference weight, baseline pressure, and safe range as a fallback when the label is missing.

Loaded vehicle weight is curb weight plus occupants and cargo. The front axle share splits that total between the front and rear axles. In placard mode, the baseline load is curb weight plus one average passenger. In preset mode, the baseline is the class reference weight with a 55% front and 45% rear split.

Formula Core:

The model adds about 1 psi for each 45 kg of added axle load, then applies small factors for surface, driving priority, and tire setup. Tire width scaling is used only in preset mode because placard mode is already tied to the vehicle's intended tire fitment.

\begin{array}{lcl} L_{total} & = & curb weight + passengers \times average passenger weight + cargo \\ L_{front} & = & L_{total} \times s \\ L_{rear} & = & L_{total} \times (1 - s) \\ P_{raw} & = & P_{base} \times f_{surface} \times f_{priority} \times f_{setup} \times f_{width} + \frac{L_{axle} - L_{baseline axle}}{45} \\ P_{target} & = & clamp (P_{raw}, P_{safe min}, P_{safe max}) \\ temperature shift & = & \frac{T_{forecast F} - T_{current F}}{10} \end{array}

s is the front axle share as a decimal. For rear axle calculations, the share is 1 minus s. In preset mode, the width factor is 235 divided by the entered tire width in millimeters; wider tires reduce that modeled pressure contribution and narrower tires raise it. In placard mode, the width factor is 1.

Default vehicle class pressure presets
Vehicle class	Baseline front/rear	Reference weight	Preset safe window
Compact / hatchback	32 / 32 psi	1300 kg	29-41 psi front and rear
Sedan	33 / 33 psi	1500 kg	29-42 psi front and rear
Wagon / CUV	34 / 36 psi	1700 kg	30-43 psi front, 31-44 psi rear
SUV	35 / 37 psi	1900 kg	31-44 psi front, 32-45 psi rear
Pickup (light load)	36 / 40 psi	2100 kg	32-44 psi front, 34-48 psi rear
EV / performance	38 / 40 psi	2000 kg	32-45 psi front, 34-46 psi rear

Car tire pressure factors and boundaries
Rule	Value or boundary	Effect
Surface factor	Rough 0.97, city 1.00, winter 1.01, highway 1.02	Softens rough-road estimates and firms steady or cold-use estimates slightly.
Priority factor	Comfort 0.97, balanced 1.00, efficiency 1.02, handling 1.04	Applies a small preference before the safe window is enforced.
Tire setup factor	All-season SL 1.00, summer 1.01, winter 1.02, XL 1.04	Models setup choices that may call for a firmer cold target.
Front axle share	Clamped from 45% to 65%	Controls how loaded vehicle weight is divided between front and rear axles.
Placard safe minimum	Maximum of 20 psi or placard minus 6 psi	Prevents the target from falling too far below the vehicle-specific anchor.
Placard safe maximum	Placard plus 7 psi, or plus 8 psi for handling priority or XL setup	Caps large increases unless a separate tire maximum is tighter.
TPMS floor	75% of placard pressure in placard mode	Flags forecast values near the common low-pressure warning point.
Target band	± max(1.5 psi, 5% of target), clipped to the safe window	Shows a practical checking range around the modeled target.

Temperature projection uses cold-soak temperature only. It does not model heat from driving, sun exposure, altitude, leak rate, nitrogen versus air, exact tire-load-table behavior, wheel damage, or tire aging.

Limitations:

Tire pressure is safety-critical, and a calculator cannot inspect the tire, wheel, valve stem, or vehicle label. Stop and verify the physical tire whenever the result asks for a large change, clips to a safe limit, conflicts with the placard, or differs from what the vehicle normally needs.

Measure and set pressure when tires are cold, before driving or after the vehicle has been parked for about three hours.
Do not use the sidewall maximum as the normal daily target.
Do not exceed tire, wheel, vehicle placard, or owner-manual limits.
Preset results should be confirmed against the actual placard before highway driving, towing, heavy cargo, or winter travel.
If one tire loses pressure faster than the others, inspect for punctures, valve leaks, rim damage, sidewall damage, or tread damage before driving at speed.

Worked Examples:

Family trip before a colder morning:

A sedan with 33 psi front, 35 psi rear, four 75 kg occupants, 90 kg of cargo, and a 55% front axle share carries more load than the driver-only baseline. With city surface, balanced priority, and all-season tires, the modeled targets are about 36.8 psi front and 38.2 psi rear. A forecast from 68°F to 38°F subtracts about 3 psi from the projected next cold reading if the tires are left unchanged.

Loaded pickup with a rear cap:

A light-load pickup preset with two 85 kg occupants and 520 kg of cargo can push the rear axle near the preset safe maximum, especially with highway use, handling priority, and XL tires. If Rear tire max is set to 46 psi, the rear target is capped at 46.0 psi and the axle note explains that the safe maximum is limiting the result.

Current readings become actions:

A placard setup with targets around 34.2 psi front and 36.0 psi rear turns current cold readings of 31 psi front and 33 psi rear into add instructions for both axles. Recheck with the gauge after inflating because the final reading matters more than the first amount added.

Input recovery:

Entering a 150 mm tire width or leaving a placard pressure blank in placard mode triggers Check your inputs and hides the axle rows. Correct the tire width to a realistic value, such as 235 mm, or enter the missing placard pressure to restore Pressure Plan, Load Map, Seasonal Drift, and JSON output.

FAQ:

Should I follow the door placard or the tire sidewall?

Use the door placard or owner manual for normal cold inflation pressure. The sidewall number is the tire's maximum pressure, not the vehicle's recommended daily pressure.

Why can front and rear targets be different?

Front and rear axles often carry different loads. Some vehicles also list different front and rear placard pressures, especially wagons, SUVs, pickups, and performance cars.

Why does colder weather lower the forecast pressure?

Cold air reduces tire pressure. The forecast estimate uses about 1 psi per 10°F, so a 30°F drop lowers the projected cold reading by about 3 psi.

Why does preset mode say to verify against the placard?

Preset mode estimates from a broad vehicle class. Placard mode is more specific because it starts from the cold pressures chosen for that exact vehicle setup.

Why did the pressure plan disappear?

The calculator needs valid loaded weight, passenger count, tire widths, temperatures, and placard pressures when placard mode is selected. Fix the warning items and the axle rows return.

Glossary:

Cold pressure: Tire pressure measured before driving warms the tire, usually before use or after a long parked rest.
Placard pressure: The vehicle manufacturer's recommended cold inflation pressure listed on the tire and loading label or in the owner manual.
Axle share: The fraction of loaded vehicle weight carried by the front axle, with the rest carried by the rear axle.
Safe window: The pressure range used to keep the modeled target from moving too far from the placard or preset limit.
TPMS floor: The placard-based low-pressure warning point used to flag forecast values near 75% of the placard pressure.
Seasonal drift: Estimated pressure change caused by a different cold-soak temperature.

References:

Tire Safety Ratings and Awareness, National Highway Traffic Safety Administration.
Winter Weather Driving Tips, National Highway Traffic Safety Administration.
49 CFR Section 571.138, Tire pressure monitoring systems, Legal Information Institute.
How Does Temperature Change Affect Tire Air Pressure?, Tire Rack.