PSI to Bar Converter

About the PSI to Bar Converter

Convert pounds per square inch (psi) to bar and bar to psi — type in either box and the other updates. A bar is exactly 100 kPa, and a psi is one pound-force on a square inch, 6,894.757 Pa, so bar = psi × 0.0689476 and psi = bar × 14.5038: 32 psi is 2.21 bar and 2.2 bar is 31.91 psi.

Under the result you also get kilopascals, kgf/cm² (the “kg/cm²” or “ksc” on many gauges), megapascals for high pressures, and what a gauge reading is in absolute pressure at sea level. Type a reading as 32 psig, 2.2 bara or 220 kPag and it stays a gauge or absolute reading. The charts convert the pressures used on car, two-wheeler, bicycle, van and truck tyres into psi, bar, kPa and kgf/cm², next to printable psi and bar charts — numbers only: the right pressure for a vehicle is the one its maker gives.

Common uses

• Tyre pressures from a placard, a manual or a pump in the other unit.
• Bicycle tyres whose sidewalls print psi and bar ranges.
• Air compressors, pressure washers and regulators rated in bar or psi.
• Gauges marked kg/cm² (kgf/cm²) next to psi.
• Diving cylinders, hydraulics and gas bottles in bar and psi.

The formula

The SI Brochure gives 1 bar = 0.1 MPa = 100,000 Pa exactly. The psi is a pound-force (0.45359237 kg × 9.80665 m/s²) per square inch (0.0254 m)², 6,894.757 Pa (NIST SP 811, Appendix B.8). So:

• bar = psi × 0.0689476 (psi ÷ 14.5038)
• psi = bar × 14.5038
• kPa = psi × 6.89476, and 1 bar = 100 kPa
• kgf/cm² = bar ÷ 0.980665 — 1 kgf/cm² is exactly 98,066.5 Pa

In your head: divide psi by 14.5 for bar (32 psi ≈ 2.2 bar), or multiply bar by 14.5 for psi.

Gauge and absolute pressure

Tyre gauges, compressor gauges and pump gauges show gauge pressure — the pressure above the air around them, written psig or barg. Absolute pressure (psia, bara) counts from a vacuum: absolute = gauge + atmospheric pressure, and the standard atmosphere is 101.325 kPa = 1.01325 bar ≈ 14.696 psi. A flat tyre reads 0 psig but holds about 14.7 psia of air.

Converting between psi and bar never changes the reference: 32 psig is 2.21 barg. Only going from gauge to absolute (or back) needs the atmospheric pressure, which falls with altitude; the Pressure Converter does that with a local value or your altitude.

Tyre pressures

Use the pressure the vehicle maker gives: the UK Highway Code, Annex 6 says tyres must be inflated to the manufacturer’s specification for the load being carried, and to check them when the tyres are cold, because warm tyres read high. The figures are in the vehicle handbook and usually on a label inside the fuel filler flap or on the driver’s door sill or pillar. On a bicycle, the tyre’s sidewall prints its range. The charts here only convert those numbers between psi, bar, kPa and kgf/cm².

Limitations

• The conversion is exact until it is rounded for display (10 significant figures, or choose a Precision).
• The tyre charts are conversion tables, not recommendations: always follow the vehicle placard or the tyre sidewall.
• The absolute-pressure line uses the standard atmosphere at sea level (101.325 kPa). At altitude, and with the weather, the real air pressure is lower or higher; use the Pressure Converter for a local value.
• kgf/cm² uses standard gravity (9.80665 m/s²), as gauges marked kg/cm² do.

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