What is Bar to PSI Pressure Converter?
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Bar to Psi Converter
Bar to PSI: 1 bar = 14.504 psi. Used in tire pressure, hydraulics, scuba diving.
About this converter
The bar is a non-SI metric unit of pressure equal to exactly 100,000 pascals; the pound per square inch (psi) is the customary US/UK unit equal to 6,894.757293168 pascals. Converting one to the other is a single fixed multiplication and the ratio never changes with temperature, altitude, or location.
The two units dominate different worlds. Bar is the everyday metric of European garages, scuba shops, and industrial hydraulics, while psi rules North American tire placards, plumbing, and compressed-air tooling. Anyone who buys a European car, dives abroad, or reads a datasheet written for the other market ends up converting, and a wrong factor here can mean an under-inflated tire or a mis-specified pump. This page handles both directions, bar to psi and psi to bar, with the exact factor.
How it works
Both units are anchored to the pascal, the SI unit of pressure (1 Pa = 1 N/m2). The defining identities are 1 bar = 105 Pa (BIPM SI Brochure, 9th ed., Table 8) and 1 psi = 6,894.757293168 Pa (NIST SP 811, App. B.8). Dividing gives the exact ratio:
1 bar = 100,000 / 6,894.757293168 psi
= 14.5037737730209... psi
1 psi = 6,894.757293168 / 100,000 bar
= 0.0689475729 bar
For tire-shop precision four decimals (14.5038) is plenty; for hydraulic and metrology work use the full 14.5037737730. A handy mental shortcut is that 1 bar is a touch over 14.5 psi, so multiplying by 14.5 and adding a fraction of a percent gets you within rounding range without a calculator. To go the other way, dividing psi by 14.5 lands close enough for a quick tire check.
Worked example
A European car owner's manual specifies a front tire pressure of 2.3 bar (cold). The owner has a US-spec gauge that only reads psi and wants the equivalent before topping up at the air pump. Convert:
- Read the input: 2.3 bar (gauge pressure, measured above atmosphere).
- Apply the factor: 2.3 x 14.5037737730 = 33.358679 psi.
- Round to gauge resolution: 33.4 psi (most analog gauges resolve to 0.5 psi).
- Inflate to 33 to 34 psi; recheck cold after the tire has been static for at least 3 hours.
Reference table
| bar | psi | Typical use |
|---|---|---|
| 0.1 bar | 1.4504 psi | Low-pressure HVAC duct |
| 1 bar | 14.5038 psi | Close to 1 atmosphere |
| 2.3 bar | 33.359 psi | Passenger car tire |
| 7 bar | 101.526 psi | Shop compressor outlet |
| 10 bar | 145.038 psi | Hydraulic supply line |
| 100 bar | 1,450.38 psi | Industrial hydraulics |
| 200 bar | 2,900.76 psi | Standard scuba tank fill |
| 1,000 bar | 14,503.8 psi | Diesel common-rail injector |
Common pitfalls
- Gauge vs absolute pressure. Tire gauges, manometers, and most industrial dials read gauge (bar-g, psig), which subtracts atmospheric pressure. Compressor inlets, vacuum specs, and physics problems use absolute (bar-a, psia). At sea level the offset is ~1.01325 bar (~14.696 psi). Specifying 100 bar without an "a" or "g" is ambiguous by 1 percent.
- Bar versus atmosphere. 1 bar = 100,000 Pa; 1 atm = 101,325 Pa. They differ by ~1.325 percent. Older meteorology references and some chemistry tables use atm; modern weather reports use millibar (mbar) or hectopascal (hPa).
- kPa, MPa, and bar mixed in the same datasheet. 1 bar = 100 kPa = 0.1 MPa. Hydraulic-equipment specs flip freely between the three; misreading 10 MPa as 10 bar is a 100x error.
- Cold vs hot tire pressure. Tire pressure rises about 0.07 bar (1 psi) per 5 degC of warming. The placard value is always cold. Reading 2.5 bar on a freeway-warm tire actually means ~2.2 bar cold.
- Psi versus psia versus psig. Unannotated "psi" almost always means gauge in tire, plumbing, and HVAC contexts but almost always means absolute in vacuum, semiconductor, and aerospace contexts. Check the field convention before converting.
Related tools and references
Frequently asked questions
What is the exact bar to psi conversion factor?
1 bar = 100,000 Pa exactly, and 1 psi = 6,894.757293168 Pa. Dividing gives 1 bar = 14.5037737730 psi. The factor is rational and exact because both units are defined in terms of the pascal (NIST SP 811).
What is the difference between gauge pressure and absolute pressure?
Gauge pressure (bar-g, psig) reads zero at local atmospheric pressure; absolute pressure (bar-a, psia) reads zero at vacuum. The two differ by ~1.01325 bar (~14.7 psi) at sea level. Tire gauges and most industrial dials show gauge; compressor inlet specs and physics use absolute. Mixing them creates a one-atmosphere error.
What tire pressure is normal in bar and psi?
Passenger car tires typically run 2.0 to 2.5 bar (29 to 36 psi) cold. Bicycle racing tires use 6 to 9 bar (87 to 130 psi). Heavy truck tires reach 7 to 8 bar (100 to 115 psi). Scuba tanks are filled to 200 to 300 bar (2,900 to 4,350 psi).
Is bar an SI unit?
No. The pascal (Pa) is the SI unit of pressure. Bar is a non-SI unit accepted for use with the SI by BIPM and is defined as exactly 100,000 Pa. Meteorologists use millibar (mbar = hPa), engineers use bar, and physicists use kilopascals or megapascals.
Sources
- BIPM (2019) The International System of Units (SI), 9th edition, Table 8 (non-SI units accepted for use with the SI).
- NIST Special Publication 811 (2008) Guide for the Use of the International System of Units, Appendix B.8 conversion factors.
- ISO 80000-4:2019 Quantities and units - Part 4: Mechanics.