Pressure converter
p = F / A
Convert a pressure between pascal, hectopascal, kilopascal, megapascal, bar, millibar, atmosphere, millimeter of mercury, torr and psi. Every factor is exact by definition, so conversion is reversible without loss, up to display rounding. What no factor settles (absolute pressure versus gauge pressure, measured above atmospheric) is explained below the tool, because that is where most misreadings of a pressure gauge come from.
Raw value: 100
1 Bar = 100 Kilopascal (kPa)
Scientific dossier
What the tool computes, what it assumes, where it stops being valid, and where its data comes from.
Method & formulasp = F / A
p = F / A
1 Pa = 1 N/m²
1 bar = 14.503773773 psi
The pascal, the SI unit. Is the pressure of a one-newton force spread over one square meter, a tiny pressure on a human scale, hence the everyday use of its multiples (hPa in meteorology, kPa and MPa in mechanics) and of inherited units such as the bar or the psi. All of them measure the same physical quantity: moving between them is a plain multiplication, with no assumption and no measurement involved.
- Pa
- · Pascal (Pa)
- hPa
- · Hectopascal (hPa)
- kPa
- · Kilopascal (kPa)
- MPa
- · Megapascal (MPa)
- bar
- · Bar
- mbar
- · Millibar (mbar)
- atm
- · Atmosphere (atm)
- mmHg
- · Millimeter of mercury (mmHg)
- Torr
- · Torr
- psi
- · Pound per square inch (psi)
The torr is defined as exactly 1/760 of a standard atmosphere, that is 101,325/760 ≈ 133.322368 Pa. The conventional millimeter of mercury is defined by a mercury column of density 13,595.1 kg/m³ under standard gravity, that is 133.322387415 Pa. The two definitions differ by 1.4 × 10⁻⁷ in relative terms, one part in seven million. With no measurable consequence in practice, blood pressure included. This tool applies the conventional mmHg value to both units: converting from the atmosphere, it therefore shows 759.999892 mmHg where the torr definition would give exactly 760. That gap comes from the definitions, not from rounding in the calculation.
Validity domainA tyre, compressor or diving-cylinder gauge almost always shows gauge pressure: the amount above atmospheric pressure, about 1.
A tyre, compressor or diving-cylinder gauge almost always shows gauge pressure: the amount above atmospheric pressure, about 1.013 bar below the absolute value at sea level. Physical tables and the ideal gas law, by contrast. Assume absolute pressure. The conversion factor is the same under either convention (this tool converts units, not references) but comparing a gauge value with an absolute one is off by a full atmosphere. Check the convention of both values before putting them side by side.