Bar to PSI Converter
Convert between bar and pounds per square inch (psi) — bidirectional, exact, no rounding tricks. 1 bar = 14.5037737730 psi; 1 psi = 0.0689475729 bar.
1 bar =
14.5
Converted via exact SI factors: 1 bar = 100 000 Pa exactly (BIPM) and 1 psi = 6894.757293168 Pa exactly (NIST SP 811, derived from 1 lbf = 4.4482216152605 N and 1 in² = 0.00064516 m² under the 1959 International Yard and Pound Agreement). So 1 bar = 14.5037737730 psi and 1 psi = 0.0689475729 bar. 1 bar × 14.5037737730 = 14.503773773021683 psi.
How to use this calculator
Type a pressure value, pick "Bar → psi" or "psi → Bar" in the Direction select, and the result updates instantly. Flip the direction to invert the conversion.
How the calculation works
Both factors are exact under the SI. 1 bar is defined as exactly 100 000 pascals (BIPM SI brochure). 1 psi is derived from the 1959 International Yard and Pound Agreement: 1 pound-force = 4.4482216152605 N exactly and 1 square inch = 0.00064516 m² exactly, giving 1 psi = 6894.757293168 Pa exactly (NIST SP 811). The ratio 100 000 / 6894.757293168 = 14.5037737730 gives psi per bar, and the reciprocal 0.0689475729 gives bar per psi.
Worked example
A car tyre pressure of 2.4 bar in psi: 2.4 × 14.5037737730 = 34.81 psi. Going back: 34.81 × 0.0689475729 = 2.400 bar, demonstrating the exact round-trip. A typical road-bike tyre at 100 psi is 100 × 0.0689475729 = 6.89 bar; a SCUBA tank at 200 bar is 200 × 14.5037737730 = 2900.75 psi.
Frequently asked questions
How many psi in 1 bar?
1 bar = 14.5037737730 psi exactly. The factor comes from the BIPM definition 1 bar = 100 000 Pa combined with the NIST definition 1 psi = 6894.757293168 Pa, both of which are exact in SI.
How many bar in 1 psi?
1 psi ≈ 0.0689475729 bar (exactly 6894.757293168 / 100 000). Equivalently, 1 psi = 68.9476 mbar — useful for weather and HVAC instruments calibrated in millibar.
Is 1 bar the same as 1 atmosphere?
Close, but not identical. 1 bar = 100 000 Pa exactly, while 1 standard atmosphere (atm) = 101 325 Pa exactly (10th CGPM, 1954). So 1 atm = 1.01325 bar = 14.6959 psi. Tyre and HVAC specs almost always use bar, not atm.
What pressure unit do car tyres use?
Most of Europe, South America, and Asia label tyre pressures in bar (or kPa). The US, UK, and Canada typically use psi. Owner manuals often print both. For example, 32 psi (a common cold-tyre target) is 2.21 bar.
Are bar and psi gauge or absolute pressure?
The unit itself is unit-agnostic — bar and psi can express either gauge pressure (above atmospheric) or absolute pressure (above perfect vacuum). When the difference matters, gauges are labelled "barg" / "psig" and absolute readings "bara" / "psia". This converter just changes units; it does not add or remove the 1 atm offset.
How accurate is this converter?
It multiplies in IEEE 754 double precision using the exact SI factor 14.5037737730209. Round-trip error is below 1 part in 10¹⁵ — far below the accuracy of any tyre gauge, manometer, or pressure transducer you are likely to use.