CalcWisp
Guides
Menu
Money & investing26Math27Unit converters211Health & fitness10Time & work5School & grades3Images & PDFs11Text & generators14Career1Everyday life4
GuidesGlossaryTemplates & planners

Bar

Also called: bar, bars

Definition: The bar is a metric unit of pressure defined as exactly 100,000 pascals (100 kPa), a little less than standard atmospheric pressure; one bar is 14.50377 psi.

Updated November 3, 2026 · How we check facts

The bar is used for tire pressure, weather maps and pressure vessels outside the United States. NIST lists it as exactly 1.0 × 10⁵ pascals. Standard atmospheric pressure is 101,325 Pa, so one bar is 0.98692 atmospheres.

Formula

kPa = bar × 100
psi = bar × 14.50377

Example

A tire at 2.5 bar is 250 kPa, or 2.5 × 14.50377 = 36.26 psi. Water systems rated at 4 bar are 400 kPa, about 58 psi. See bar to psi and psi to bar, and pounds per square inch.

Related terms

Pounds per Square Inch (psi)Psi is the US customary unit of pressure: one pound-force acting on one square inch, equal to 6,894.757 pascals or 6.894757 kilopascals.International System of Units (SI)The International System of Units (SI) is the modern metric system: seven base units, including the meter, kilogram, second and kelvin, with prefixes that scale by powers of ten.Acre (ac)The acre is a US customary unit of area equal to exactly 43,560 square feet, 4,840 square yards or 160 square rods; NIST gives it as 4,046.8564224 square meters.Centimeter (cm)The centimeter is a metric unit of length equal to one hundredth of a meter (0.01 m); exactly 2.54 centimeters make one inch.Cubic Foot (ft³)The cubic foot is a volume unit equal to a cube 1 foot on each side: 1,728 cubic inches, 0.02831685 cubic meters, about 28.317 liters or 7.48 US gallons.Cubic Meter (m³)The cubic meter is the SI unit of volume: a cube 1 meter on each side, equal to 1,000 liters, 1,000,000 cubic centimeters, 35.315 cubic feet or 1.308 cubic yards.Cubic Yard (yd³)The cubic yard is a volume unit equal to a cube 1 yard on each side: 27 cubic feet, 46,656 cubic inches, 0.7645549 cubic meters or about 764.55 liters.Fluid Ounce (fl oz)A fluid ounce is a unit of volume; one US fluid ounce is 29.57353 milliliters, and 8 of them make a US cup. It is not the same as the ounce used to weigh things.

Sources

  1. NIST Guide to the SI (SP 811), Appendix B.8 — Factors for Units Listed Alphabetically