Article — Pressure Converter
Pressure Converter: Bar to Pa, kPa, MPa, psi, atm, mmHg, inHg, torr
A universal pressure converter translates bar (the metric working unit) into ten target units: Pa, kPa, MPa, mbar, atm, psi, mmHg, inHg, torr, and kg/cm². 1 bar = 100,000 Pa = 14.504 psi = 0.9869 atm = 750.062 mmHg. All factors are exact international standards.
Different industries default to different pressure units. Tire pressure is reported in psi in the U.S. and bar in Europe. Blood pressure uses mmHg. Weather pressure uses hPa (= mbar). Industrial hydraulics use MPa or bar. A universal pressure converter handles all the cross-translations through a single consistent base.
Pressure converter units explained
The pascal is SI base. The bar is metric working unit (100,000 Pa). The atmosphere is the historical sea-level reference (101,325 Pa). The pound per square inch is U.S. imperial (6894.76 Pa). The millimeter of mercury is from the old mercury barometer (133.322 Pa). The torr (1/760 atm) is the laboratory vacuum unit. The kilogram per square centimeter (kg/cm²) is the older European technical atmosphere (98,066.5 Pa).
Each unit emerged from a different industry or experimental tradition. The pressure converter rationalizes them through exact factors against the bar, which sits at a comfortable midpoint between micrometeorological pressures and high-pressure hydraulics.
The bar was originally defined in 1909 by Norwegian meteorologist Vilhelm Bjerknes as exactly 10^6 dyn/cm² (a CGS unit equal to 100,000 Pa in SI). He wanted a clean meteorological pressure unit close to atmospheric pressure but free of the awkward 101,325 of the atmosphere. Today the bar persists in industry — especially European hydraulics — even though it sits just outside the strict SI list.
Why use bar as the base
The bar makes a good pressure converter base because 1 bar = 100,000 Pa exactly, so SI-prefix conversions are clean factors of ten. 1 bar = 100 kPa = 0.1 MPa = 1000 mbar. The relationships are decimal shifts, no awkward decimals.
For imperial conversions, 1 bar = 14.5038 psi. For the standard atmosphere, 1 bar = 0.98692 atm (close to 1, off by 1.3%). For mmHg, 1 bar = 750.062 mmHg. None of these factors is exactly round, but they sit at convenient working magnitudes. A pressure converter built around the bar handles every common pressure regime without scientific notation.
Pressure converter for psi and imperial units
The pound per square inch (psi) is the U.S. imperial pressure unit. 1 psi = 6894.757 Pa = 0.06895 bar. The pressure converter takes bar values and gives psi values that engineering drawings, pressure-vessel codes, and ASME standards all use. A 14 bar steam line is 203 psi; a 200 bar hydraulic system is 2901 psi.
The inch of mercury (inHg) is U.S. aviation and weather. 1 inHg = 3386.39 Pa = 0.03386 bar. Standard sea-level altimeter setting is 29.92 inHg = 1.01325 bar. The pressure converter translates between aviation forms (inHg) and meteorological forms (mbar/hPa) cleanly: 1 hPa = 1 mbar, and 1 mbar = 0.02953 inHg.
Pressure converter for atm, mmHg, inHg, torr
The atmosphere is fixed at 101,325 Pa = 1.01325 bar. It is the natural reference for chemistry, physiology, and diving — physical conditions where Earth's surface pressure is the meaningful baseline. The pressure converter goes between bar and atm with a simple factor (0.987 atm per bar).
The mmHg and torr are laboratory and medical units. They are effectively identical (differ by 0.00002%) but defined slightly differently. The torr is 1/760 of an atm; the mmHg is a mercury column at standard gravity. Blood pressure is reported in mmHg; vacuum chambers report in torr. The pressure converter accepts either name with the same factor.
1 bar = 100,000 Pa 1 bar = 100 kPa = 0.1 MPa1 bar = 14.504 psi 1 bar = 0.9869 atm1 bar = 750.06 mmHg 1 bar = 29.53 inHg1 atm = 1.01325 bar 1 psi = 0.06895 barPressure converter in tire and bike pressure
Car tires inflate to 2.0–2.5 bar (29–36 psi). European cars print bar on the door-jamb sticker; U.S. cars print psi. The pressure converter bridges the two for travelers and rental fleets. 32 psi (the most common U.S. spec) is 2.2 bar; 35 psi is 2.4 bar.
Road bikes run higher: 6–8 bar (87–116 psi). Tubeless mountain bikes run lower: 1.5–2.5 bar (22–36 psi). Truck and bus tires reach 7–8 bar (101–116 psi). Knowing the bar value of a given psi reading or vice versa avoids over-inflation when using a pump calibrated to the other scale.
Pressure converter for water depth
Water adds about 1 bar per 10 meters of depth — more precisely, 0.0981 bar per meter for freshwater (and 0.1006 bar per meter for seawater, which is denser). A diver at 30 m feels 3 bar of water pressure on top of the 1 atm atmospheric. Total absolute pressure: about 4 bar = 3.95 atm = 400 kPa = 58 psi.
The pressure converter handles the conversion neatly. The water-depth rule of 1 bar per 10 m is exact to within 1% for freshwater and within 0.5% for seawater. Pool depths translate to pressure: 5 m at the bottom of a deep pool is 0.5 bar gauge above atmosphere, or 7.3 psi gauge.
Equipment ratings are usually gauge pressure (above atmosphere). A 10-bar pressure vessel rating is 10 bar gauge, meaning 11 bar absolute. The pressure converter computes absolute values, so subtract 1.01325 bar (atmospheric) to compare with a gauge reading. The difference matters most at low pressures.
Common pressure converter mistakes
The first mistake is treating bar and atm as identical. They differ by 1.3% (1 atm = 1.01325 bar). For tire pressure or weather, the difference is negligible; for laboratory or aerospace work, it matters.
The second mistake is conflating psi and psig. A pressure converter that gives psi values is reporting absolute psi. Equipment gauges read psig (gauge), 14.7 psi lower at sea level. Translating between the two requires subtracting or adding the atmospheric offset.
The third mistake is misreading kg/cm² as kg/m² (or kgf/cm² as a force unit). 1 kg/cm² = 98,066.5 Pa = 0.9807 bar = 14.223 psi. The pressure converter handles kg/cm² correctly, but readers used to other units sometimes underestimate it by failing to recognize that the unit is a pressure, not a mass-per-area density.
- 1 bar = 100,000 Pa (exact)
- 1 bar = 14.5038 psi
- 1 atm = 1.01325 bar = 101,325 Pa
- 1 psi = 0.06895 bar = 6894.76 Pa
- Car tire ≈ 2.2 bar = 32 psi gauge
- Sea-level standard = 1.013 bar = 14.7 psi atmospheric
- Water depth = ~1 bar per 10 m
- kg/cm² = 0.9807 bar = 14.223 psi
For quick mental conversions, 1 bar ≈ 14.5 psi. Multiply bar by 15 for a rough psi value, then subtract 3% — 2 bar × 15 = 30 psi, minus 3% = 29.1 psi (exact 29.0). Going the other way, divide psi by 15 for a rough bar value. Adequate for everyday work; use the calculator for precise specs.