Pressure Converter

How to use the pressure converter

Choose the unit you have in From and the unit you want in To, type the value and press Convert. Negative values are accepted, because a gauge reading below atmospheric pressure, such as a partial vacuum, is negative.

How pressure conversion works

Pressure is force per unit area. The SI unit is the pascal (Pa), one newton per square meter, and every unit here is a fixed multiple of it. The converter changes your value to pascals and then to the target unit. The key definitions are:

• Bar: exactly 100,000 Pa, so 1 bar is 100 kPa and 1 millibar equals 1 hectopascal.
• Standard atmosphere (atm): exactly 101,325 Pa, which is 1.01325 bar.
• Pound per square inch (psi): one pound-force on one square inch, about 6,894.757 Pa.
• Technical atmosphere (at, kgf/cm²): exactly 98,066.5 Pa.
• Torr: exactly 1/760 of a standard atmosphere, about 133.322 Pa.
• Mercury and water columns: the conventional values from NIST SP 811, which use standard gravity and a fixed density, so they do not depend on temperature. For water that density is 1,000 kg/m³, giving 1 inH₂O = 249.08891 Pa.

Common pressure conversion factors

Multiply a value in the first unit by the factor to get the second unit.

Worked examples

• 2.2 bar to psi: 2.2 × 14.503774 ≈ 31.91 psi.
• 32 psi to bar and kPa: 32 × 0.068948 ≈ 2.21 bar, or 32 × 6.894757 ≈ 220.63 kPa.
• 200 bar to psi (a figure found on scuba cylinders): 200 × 14.503774 ≈ 2,900.75 psi.
• 1013.25 hPa to inHg (standard sea-level pressure on an altimeter): 1013.25 × 0.02953 ≈ 29.92 inHg.

Bar to psi and kPa

Psi to bar and kPa

One standard atmosphere in other units

Gauge pressure versus absolute pressure

Most everyday gauges, including tyre gauges and the gauges on compressors and gas regulators, read gauge pressure: the pressure above the surrounding atmosphere. Absolute pressure is measured from a perfect vacuum. Absolute pressure equals gauge pressure plus the atmospheric pressure at that moment and place.

In US practice this is often marked on the unit: psig for gauge and psia for absolute. With a standard atmosphere of about 14.696 psi, a reading of 32 psig is about 46.70 psia. Real atmospheric pressure changes with the weather and falls with altitude, so for precise work use the measured value rather than the standard one.

This converter changes units only. It does not add or remove atmospheric pressure, so convert psig to bar and you get a gauge value in bar, often written barg. A gauge reading of −0.8 bar, a partial vacuum, is −80 kPa or about −11.60 psi.

Where the other units appear

• hPa and mbar are used for air pressure in weather reports; they are the same size.
• inHg is used for altimeter settings and weather reports in the United States; standard pressure is about 29.92 inHg.
• mmHg is used for blood pressure. A reading of 120/80 mmHg is about 16.0/10.7 kPa.
• inH₂O and mmH₂O are used for small pressure differences, such as across ventilation filters and in ductwork.
• MPa and ksi are used for material strengths and hydraulic systems; 1 ksi is about 6.895 MPa.

Common pitfalls

• Treating kgf/cm² as bar. A technical atmosphere is about 1.93% smaller than a bar. The difference is small but matters for calibration and safety margins.
• Assuming torr and mmHg differ meaningfully. They differ by less than one part in a million, so either is fine outside metrology.
• Mixing water-column conventions. Some references and instruments base inches of water on water at a stated temperature, such as 4 °C or 60 °F, which gives slightly different factors from the conventional value used here.

Frequently asked questions

How many psi are in one bar?

About 14.5038 psi. One psi is about 0.0689 bar.

Is 1 bar the same as 1 atmosphere?

Close, but no. One standard atmosphere is 1.01325 bar, so a bar is about 1.3% smaller.

What is the difference between psi and psig?

The unit is the same size. "psig" says the value is gauge pressure, measured above atmospheric pressure; "psia" says it is absolute. Convert the number as psi, and add or subtract atmospheric pressure separately if you need to switch between gauge and absolute.

How much does pressure rise with depth when diving?

In seawater, roughly 1 bar for every 10 meters of depth, on top of the atmospheric pressure at the surface. The exact figure depends on the water's density.

Supported units

• Pascal (Pa)
• Hectopascal (hPa)
• Kilopascal (kPa)
• Megapascal (MPa)
• Gigapascal (GPa)
• Bar (bar)
• Millibar (mbar)
• Standard atmosphere (atm)
• Technical atmosphere (kgf/cm²) (at)
• Pound per square inch (psi)
• Kilopound per square inch (ksi)
• Pound per square foot (psf)
• Torr (Torr)
• Millimeter of mercury (mmHg)
• Inch of mercury (inHg)
• Centimeter of water (cmH₂O)
• Millimeter of water (mmH₂O)
• Inch of water (inH₂O)
• Dyne per square centimeter (dyn/cm²)