Tyre inflation calculator
Enter “current|target” tyre pressure to convert between PSI, BAR and KPA and see exactly how much air to add, with temperature correction.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Inflation plan
The target in four units, converted to the current temperature, plus the top-up needed.
Enter “current|target” to calculate
Target kPa: 0
What this tool does
- Convert a PSI placard into the BAR your pump shows, and see how much to add.
- Check whether hot motorway readings really exceed the cold specification.
- Work out the seasonal top-up when ambient temperature drops from 20 °C to 5 °C.
Example
Input
2.2|2.4
Output
当前 2.2 bar，目标 2.4 bar（冷胎 20 °C 下的目标）：需要补气 0.240935 bar 当前读数（bar） = 2.2 bar 目标冷胎胎压（bar） = 2.4 bar 磅力每平方英寸 (psi) = 34.809057 psi 巴 (bar) = 2.4 bar 千帕 (kPa) = 240 kPa 千克力每平方厘米 (kgf/cm²) = 2.447319 kgf/cm² 折算到 25 °C 时要打的读数 = 2.440935 bar 需要补充 = 0.240935 bar（24.093468 kPa） 折算基准：1 psi = 6.894757293168361 kPa，1 bar = 100 kPa；温度修正按等容关系 P₂ = P₁ × (T₂ + 273.15) ÷ (T₁ + 273.15)。 气泵表普遍有 ±5% 误差，建议打到目标后隔天冷胎复测一次；带胎压监测（TPMS）的车可直接看仪表读数。
At 32 psi with a 35 psi cold target (20 °C), inflate to about 35.597 psi at 25 °C — a 3.597 psi top-up.
Frequently asked questions
What input format is expected?
Two numbers separated by a pipe or space: current|target, e.g. 32|35 or “2.2 2.4”, both in the unit you select (psi by default). Use the placard cold pressure as the target.
Why correct for temperature?
Pressure changes about 3.4% per 10 °C by the ideal-gas relationship. The placard gives a cold value while you may be inflating at 25 °C or right after a motorway run, so the target must be converted to the current temperature.
Will the result be exact?
Pumps are typically accurate to ±5%, so recheck cold the next day. A TPMS readout is usually steadier than a handheld gauge.
What does a negative top-up mean?
The current reading is above target, so you need to let air out instead of adding it. The tool states that explicitly.
Keywords：轮胎打气胎压计算器PSI BAR KPA胎压单位换算补气多少tyre pressure轮胎气压温度折算