PSI Converter

The PSI Converter is a unit-family page for pressure values that start in pounds per square inch. Enter one psi value and the form shows kilopascals, bar, atmospheres, megapascals, millimeters of mercury, and pascals. That makes it different from the general pressure converter, where you choose both a source and a target unit. Here the source is fixed as psi, which is faster for tire gauges, plumbing gauges, compressed-air tools, pressure washers, and U.S. equipment manuals.

Psi is familiar because it appears directly on many physical gauges. A tire may be set to 32 psi, a compressor regulator may be adjusted to 90 psi, and a home water system may run near 50 psi. Scientific and international documents often use kPa, bar, MPa, or Pa instead. This page bridges those contexts while keeping the pressure reference, such as gauge or absolute, attached to the number.

How to use this psi conversion page

Enter a nonnegative pressure in psi. The default is 32 psi, a common passenger-car tire example. The primary result is kilopascals, and the detail rows show bar, atm, MPa, mmHg, and Pa. If you only need the bar and psi pair in both directions, use bar to PSI. If your starting value is kPa, use kPa to psi conversion. If your value starts in pascals, use pascal conversion.

The calculator is intended for unit conversion, not for selecting a safe operating pressure. Always follow the tire placard, equipment manual, pressure-relief rating, or engineering specification that applies to the actual device.

Definitions behind psi

Pressure is force per area. The pascal is the SI pressure unit:

$1\ \text{Pa} = 1\ \frac{\text{N}}{\text{m}^{2}}$

Psi uses pound-force and square inches instead. The calculator converts psi to SI units using:

$1\ \text{psi} = 6{,}894.757293168\ \text{Pa}$

From pascals, the form derives kPa, bar, atm, MPa, and mmHg. One bar is 100,000 Pa, one standard atmosphere is 101,325 Pa, and one megapascal is 1,000,000 Pa. Millimeters of mercury are useful for vacuum and older instrument references.

Formula used

The primary output is kilopascals:

$\text{kPa} = \text{psi} \times 6.894757293168$

The other rows use these conversion constants:

$\text{bar} = \text{psi} \times 0.06894757293168$

$\text{atm} = \text{psi} \times 0.06804596390977$

$\text{MPa} = \text{psi} \times 0.006894757293168$

$\text{mmHg} = \text{psi} \times 51.71493257215$

$\text{Pa} = \text{kPa} \times 1{,}000$

Worked example: 32 psi tire pressure

With the default input of 32 psi, the calculator multiplies by the kPa factor:

$32 \times 6.894757293168 = 220.632233381376\ \text{kPa}$

The primary result displays 220.6322 kPa. The supporting rows show 2.206322 bar, 2.177471 atm, 0.220632 MPa, 1,654.878 mmHg, and 220,632.23 Pa. The note summarizes the same pressure as 32 psi equals 220.6322 kPa, 2.206322 bar, or 2.177471 atm. For an actual tire gauge, you would usually round to 221 kPa, 2.21 bar, or 32 psi because the original reading is not exact to six decimals.

Reference table

Domains where psi is common

Tires are the everyday example. U.S. vehicle placards usually list psi, sometimes with kPa. The pressure is gauge pressure, measured above ambient atmosphere, and should be checked cold if the manufacturer specifies cold inflation. Air compressors and pneumatic tools also use psi gauge values, with regulators, tanks, and hoses rated for safe maximum pressures. Home plumbing and water systems often use psi, while engineering documents may convert the same values to kPa or bar.

Vacuum work needs extra care. A gauge may show negative psi relative to atmosphere, inches of mercury, torr, or absolute pressure. This calculator accepts nonnegative psi inputs and reports equivalent positive pressure magnitudes; it does not interpret signed vacuum gauge readings. For atmosphere-centered comparisons, use ATM conversion after deciding whether your pressure is absolute.

Precision and pitfalls

The displayed values are useful for calculations, but the source controls meaningful precision. A tire gauge marked in whole psi cannot create a truly six-decimal bar value. Keep extra digits while converting between units, then round according to the instrument or specification. Do not confuse psi with ksi, which is one thousand psi and appears in stress and materials contexts. Most importantly, preserve the reference label. A reading in psig remains gauge pressure after conversion to kPa or bar; it does not become absolute pressure automatically.

Accuracy and limits

The calculator derives every output from pascals. The mmHg row uses the NIST conventional 0 °C factor and must not be read as exact torr.

Sources

• NIST, SI Units — SI pressure-unit framework and pascal context.
• NIST, Special Publication 811 — conversion-factor guidance for SI and customary pressure units.
• NOAA Ocean Service, What is a barometer? — background on atmospheric pressure measurement.