Pressure Converter
Convert pressure across PSI, Bar, kPa, atm, and inHg — covers tyres, oil, boost, and vacuum readings.
Multi-Unit Pressure Converter
PSI ⇄ Bar ⇄ kPa ⇄ atm ⇄ inHg
How It Works
All pressure units are converted through kPa as the SI reference. 1 atm = 101.325 kPa = 14.696 PSI = 1.01325 bar = 29.921 inHg.
How to Use This Calculator
- Enter the pressure value in any one field.
- Click Convert — all five units update simultaneously.
- Use PSI for North American tyre gauges, bar for European gauges, kPa for many door placards.
- Use atm for atmospheric reference; inHg for vacuum and weather readings.
- Note: tyre pressures are gauge pressure; atmospheric readings are absolute pressure.
Worked Example
Reference Table
| PSI | Bar | kPa | Application |
|---|---|---|---|
| 0.0 | 0.000 | 0.0 | Vacuum (perfect) |
| 14.7 | 1.013 | 101.3 | 1 atm (atmospheric) |
| 28 | 1.930 | 193.0 | Low tyre pressure (passenger car) |
| 32 | 2.207 | 220.7 | Normal tyre pressure |
| 35 | 2.413 | 241.3 | Performance tyre setting |
| 45 | 3.103 | 310.3 | Max tyre sidewall (typical) |
| 50 | 3.447 | 344.7 | High boost turbo pressure |
Frequently Asked Questions
What is the difference between gauge pressure and absolute pressure?
Gauge pressure is measured relative to atmospheric pressure (0 PSI gauge = 1 atm absolute). Absolute pressure includes atmospheric. Tyre pressures and boost gauges use gauge pressure. Altitude charts and weather use absolute pressure.
Why is vacuum measured in inHg?
InHg (inches of mercury) was historically used in weather instruments and vacuum measurement. Car diagnostic vacuum tests (intake manifold, brake booster) are often measured in inHg. At sea level, perfect vacuum = 29.92 inHg absolute, or 0 inHg gauge.
What boost pressure is typical for a street performance car?
Street-tuned turbocharged cars typically run 8–15 PSI (0.55–1.03 bar) of boost gauge pressure. Competition engines can run 20–40 PSI. High boost requires intercooling, upgraded injectors, and internal engine reinforcement.
How does altitude affect boost pressure readings?
At altitude, atmospheric pressure is lower. A gauge reading of 14 PSI at sea level (total 28.7 PSI absolute) becomes the same 14 PSI gauge reading at altitude but from a lower absolute baseline. Boost controllers reference gauge pressure and may behave differently at altitude.
