Pressure Converter (Pa, kPa, MPa, bar)

Understanding the pressure converter — concept and principle

This converter changes a pressure value between pascals, kilopascals, megapascals, bar, millibar (hPa), standard atmospheres, kgf/cm², psi, torr, mmHg, mmH₂O, inH₂O, inHg and microns. Use it for tyre and gas-cylinder pressures, hydraulic and pneumatic specifications, weather reports, vacuum work or blood-pressure units.

Pressure is force per area; 1 bar is a round 100 kPa, close to air pressure at sea level.

How it is calculated

Every unit goes through the SI unit, the pascal (1 Pa = 1 N/m²):

result = value × (pascals per "from" unit) ÷ (pascals per "to" unit)

1 kPa = 1,000 Pa; 1 MPa = 10⁶ Pa; 1 bar = 100,000 Pa; 1 hPa = 1 mbar = 100 Pa.
1 atm = 101,325 Pa exactly; 1 torr = 101,325 ÷ 760 Pa.
1 kgf/cm² = 98,066.5 Pa; 1 psi = 6,894.757293 Pa.
Conventional mmHg and mmH₂O are defined with standard gravity (9.80665 m/s²).

The principle

Pressure is force divided by area. Different fields picked different forces and areas: newtons per square metre (Pa), pound-force per square inch (psi), kilogram-force per square centimetre (kgf/cm²). Liquid-column units such as mmHg come from the height of mercury or water that the pressure can hold up, using p = ρgh. The bar was chosen as a round 100 kPa, close to atmospheric pressure, so 1 bar ≈ 0.987 atm ≈ 1.02 kgf/cm².

Worked example

Default inputs: 1 bar to kilopascals.

Convert to pascals: 1 bar = 100,000 Pa.
Divide by the size of 1 kPa (1,000 Pa): 100,000 ÷ 1,000 = 100 kPa.
The same 1 bar is 0.1 MPa, 1,000 hPa, 100,000 ÷ 101,325 = 0.9869232667 atm, 100,000 ÷ 6,894.757293 = 14.50377377 psi and 100,000 ÷ 98,066.5 = 1.019716213 kgf/cm².

How to read the result

Mean sea-level air pressure is about 1,013 hPa. Car tyres are typically around 200–250 kPa above atmospheric, and household water supply a few bar. Many gauges read gauge pressure (above atmospheric) rather than absolute pressure; absolute = gauge + local atmospheric pressure. Torr and mmHg differ by only about one part in seven million, so they can be treated as equal in practice.

Common mistakes

Mixing gauge and absolute pressure, especially with vacuum or gas laws.
Treating kgf/cm² as exactly equal to bar or atm; they differ by about 2%.
Converting MPa to N/mm² as if they differed; they are the same unit.
Treating hPa values in weather reports as gauge pressure; they are absolute.

Keep in mind: The conversion is exact, but pressure equipment must be rated and tested to the applicable codes. Never exceed a vessel's or hose's rated pressure.

Frequently asked questions

How many kPa are in 1 bar?

100 kPa.

How many MPa is 1 bar?

0.1 MPa.

Is 1 bar the same as 1 atmosphere?

Nearly. 1 atm is 1.01325 bar.

What is kgf/cm² in bar?

1 kgf/cm² = 0.980665 bar.

Sources: BIPM, The International System of Units (SI Brochure), 9th edition · NIST Special Publication 811 (2008), Appendix B

Checked 8 Nov 2026. Factors from the SI Brochure (BIPM, 9th ed.) and NIST Special Publication 811 (2008), Appendix B.