psi to bar Calculator - Convert Tyre & Gauge Pressure

About the psi to bar Calculator

Tyre pressures, compressors, pumps, pressure washers and scuba gauges are marked in psi — pounds per square inch — in the United States, and in bar across most of Europe and much of the rest of the world. Many gauges show both scales, but car handbooks, bike tyres and equipment manuals often give only one. Setting a tyre or a compressor correctly means converting between them accurately.

This psi to bar calculator converts psi to bar exactly. It also shows the pressure in kilopascals and megapascals, in standard atmospheres, and — because most everyday readings are gauge pressures — the absolute pressure the gauge reading corresponds to.

How to Use the psi to bar Calculator

Enter the pressure in psi, as shown on the gauge, pump or handbook.

The bar value appears straight away, along with kPa, MPa, atmospheres and the absolute pressure.

The Formula

  1 psi = 6,894.757 Pa          (one pound-force per square inch)
  1 bar = 100,000 Pa

  bar = psi × 6,894.757 ÷ 100,000
      = psi × 0.0689476
      ≈ psi ÷ 14.5038

The psi comes from the international pound and inch and standard gravity, so the factor is fixed to many decimal places. Dividing by 14.5 gives an answer within about 0.03 percent — close enough for any tyre.

Step-by-Step Example

32 psi, a typical car tyre pressure.

  32 × 6,894.757 = 220,632 Pa
  220,632 ÷ 100,000 = 2.20632 bar

So 32 psi is 2.20632 bar, usually rounded to 2.2 bar on a pump, or 220.6 kPa. As a gauge reading, the air inside the tyre is actually at about 3.22 bar absolute, because the atmosphere adds 1.013 bar on top.

Quick Reference

  20 psi  = 1.379 bar          40 psi  = 2.758 bar
  26 psi  = 1.793 bar          45 psi  = 3.103 bar
  30 psi  = 2.068 bar          60 psi  = 4.137 bar
  32 psi  = 2.206 bar          80 psi  = 5.516 bar
  35 psi  = 2.413 bar          100 psi = 6.895 bar

Gauge and Absolute Pressure

Almost every pressure gauge you meet in daily life — tyre gauges, compressor dials, water pressure gauges — shows gauge pressure, the difference between the pressure inside and the surrounding air. A flat tyre reads zero, even though it still contains air at atmospheric pressure. Absolute pressure adds the atmosphere back: about 14.7 psi or 1.013 bar at sea level. Science and engineering calculations such as gas laws need absolute pressure, and specifications sometimes mark the difference with psig and psia, or bar(g) and bar(a). Convert like with like: gauge psi to gauge bar.

Tyre Pressures

Car tyres are usually inflated to about 2.0 to 2.5 bar, 29 to 36 psi, as shown on a sticker inside the driver's door or fuel flap. Loaded vehicles and motorway driving often call for slightly higher pressures. Always check tyres cold, before driving, because pressure rises as they warm up: a tyre can read 2 to 4 psi, 0.15 to 0.3 bar, higher after a long drive. Bicycle tyres run much higher: road bikes often use 80 to 110 psi, 5.5 to 7.6 bar, while mountain bikes may use as little as 25 psi, 1.7 bar.

Compressors, Washers and Diving

Air compressors for workshops commonly deliver 90 to 150 psi, about 6 to 10 bar. Pressure washers are rated in bar or psi, typically 100 to 150 bar, 1,450 to 2,175 psi, for domestic models. Scuba cylinders are filled to around 200 to 300 bar, which is 2,900 to 4,350 psi. Each of these uses the same conversion, and the absolute figure matters most for diving, where gas volume depends on absolute pressure.

Other Units

Pressure appears in many other units. Kilopascals are common in car handbooks and weather: 1 bar is 100 kPa. Atmospheres are used in science and diving: 1 atm is 1.01325 bar. Millibars, or hectopascals, appear on weather maps: 1 bar is 1,000 mbar. The calculator gives kPa, MPa and atmospheres alongside bar so you can match whatever unit a gauge or manual uses.

Altitude and Temperature

Gauge readings change with conditions even when no air is added or lost. Air pressure falls with height, so a tyre filled at sea level reads slightly higher on a mountain pass, because the surrounding atmosphere pushing back is weaker: at 2,000 metres the air pressure is about 0.8 bar instead of 1.01. Temperature matters more day to day. A tyre loses roughly 1 psi, about 0.07 bar, for every 5 to 6 °C drop in temperature, so tyres set on a warm afternoon can be noticeably low on a cold morning. Check and adjust pressures regularly, especially when the seasons change.

Understanding Your Result

The headline is the pressure in bar.

The kPa and MPa line gives the same pressure in kilopascals and megapascals.

The atmospheres line compares the pressure with a standard atmosphere.

The absolute pressure line adds one atmosphere, for when the psi figure is a gauge reading.

When Should You Use This Calculator?

Use it to set tyre pressures when the pump and the handbook use different units.

Use it for compressors, pressure washers, pumps and air tools.

Use it for bicycle tyres, sports balls and inflatables.

Use it for diving and engineering specifications in psi or bar.

Common Mistakes

Mixing gauge and absolute pressure. Add one atmosphere only when you need the absolute figure.

Confusing bar and atm. One standard atmosphere is 1.01325 bar, slightly more.

Using kPa as bar. 220 kPa is 2.2 bar, not 220 bar.

Checking tyres hot. Pressure rises as tyres warm, so measure them cold.

Rounding 14.5 to 15. That makes the bar figure about 3 percent too low, enough to under-inflate a tyre noticeably.