Pressure Converter — Pa, bar, psi, atm and torr

Background.

Pressure is force distributed over area. The pascal is the coherent SI unit, but weather, tyres, hydraulics, vacuum systems and older instruments use bar, pounds per square inch, atmospheres, torr or mercury-column units. This converter puts a stated pressure on one pascal scale and changes the unit without changing the reference basis.

One pascal is one newton per square metre. Kilopascal and megapascal add exact powers of ten. Bar is exactly 100,000 Pa and millibar exactly 100 Pa; one millibar therefore has the same numerical size as one hectopascal. The standard atmosphere is defined as exactly 101,325 Pa.

Pounds per square inch combines exact pound-force and square-inch definitions, giving 6,894.757293168361 Pa per psi. The square on the length is essential. This is why a simple pound or inch conversion cannot handle pressure independently.

Torr is exactly one seven-hundred-sixtieth of a standard atmosphere. That makes 760 torr exactly 101,325 Pa. Conventional millimetre of mercury is based on a specified mercury density and standard gravity and equals 133.322387415 Pa in the factor used here. It is extremely close to torr but not identical. The page keeps separate selectors so high-precision work does not silently merge definitions.

Conventional inch of mercury likewise uses a named reference convention, here 3,386.389 Pa. A physical mercury column changes with temperature, local gravity and density, so the conventional unit should not be mistaken for a live instrument correction. Kilogram-force per square centimetre uses standard gravity and equals 98,066.5 Pa.

Conversion multiplies the input by pascals per source unit, then divides by the target factor. Every supporting result comes from the same unrounded canonical value. Decimal.js performs all arithmetic, and numbers round once at ten decimal places.

The worked example converts one standard atmosphere to exactly 101,325 Pa, 101.325 kPa, 1.01325 bar and 760 torr. It is approximately 14.6959487755 psi. Those are unit equivalences, not a claim that current local atmospheric pressure equals the defined standard atmosphere.

Negative values require context. Absolute pressure cannot fall below zero, but gauge pressure is measured relative to an ambient or chosen reference and can be negative, as in a partial vacuum. The calculator therefore preserves negative input while warning that the reference basis must remain attached. It does not convert gauge to absolute pressure automatically.

Pressure and stress share the pascal dimension but have different context. Fluid pressure acts through a field, while mechanical stress describes internal force over an oriented area. Unit conversion is identical, but this page does not calculate principal stress, allowable stress or material capacity.

Likewise, blood-pressure millimetres of mercury are clinical measurements, not a reason to use this generic page for diagnosis. It converts the unit only and supplies no interpretation. The dedicated health pages retain their measurement framing.

The live pressure solver should be used when force or area is unknown. Water-pressure-at-depth, osmotic-pressure and partial-pressure calculators derive pressure from domain inputs. This converter starts only after a pressure value and its reference convention are already known.

Displayed digits describe factor precision, not sensor accuracy. Tyre gauges, barometers and transducers have calibration uncertainty. Retain the source significant figures, instrument conditions and whether the number is absolute, gauge or differential whenever the converted result supports a decision.

What is pressure converter?

A pressure converter changes force-per-area units while preserving the pressure and its reference basis. Pascal is N/m². Bar and atmosphere are defined scales; psi combines pound-force with square inches; torr and conventional mercury-column units are close but separately defined.

How to use this calculator.

1. 01Enter the pressure and choose the exact source unit.
2. 02Choose the target unit, keeping torr separate from conventional mmHg.
3. 03Read pascals or kilopascals as the canonical check.
4. 04Retain whether the value is absolute, gauge or differential.
5. 05Apply sensor calibration and process limits separately; conversion does not validate them.

The formula.

Each unit is assigned pascals per unit. Multiply by the source factor and divide by the target factor. Torr is computed from exact atmosphere divided by 760; mmHg uses its separate conventional factor.

For 1 atm, canonical pressure is exactly 101,325 Pa. Dividing by 100,000 gives 1.01325 bar, by 101,325/760 gives exactly 760 torr, and by 6,894.757293168361 gives 14.6959487755 psi after final rounding.

A worked example.

Frequently asked questions.

References& sources.

1. [1]NIST SP 811 Appendix B.6 supplies pressure factors for atmosphere, bar, psi, torr, mercury columns and kgf/cm².
2. [2]BIPM SI Brochure defines pascal as newton per square metre.
3. [3]NIST SP 330 independently lists the pascal SI derived unit.
4. [4]NIST Handbook 44 Appendix C provides customary/SI legal-metrology relationships.
5. [5]NOAA National Weather Service glossary provides atmospheric millibar/hectopascal context.