Pressure Conversion

How to use this pressure conversion calculator

What this calculator does

This calculator converts one pressure reading into equivalent values in bar, pounds per square inch, standard atmospheres, pascals, kilopascals, hectopascals, megapascals, millimeters of mercury, and torr. It uses the pascal as the canonical internal unit, so every displayed number describes the same pressure rather than a separate measurement. The conversion is an exact unit translation when the unit definition is exact, subject only to displayed rounding. It does not determine whether a pressure is safe for a tire, vessel, pipe, medical situation, or process; those limits depend on equipment ratings and domain-specific guidance.

The pascal is the SI derived unit of pressure, equal to one newton per square meter. The current SI framework is documented in the BIPM SI Brochure, while U.S. conversion factors for common pressure units are tabulated by NIST.

When to use it

• Translate a tire, compressor, or pneumatic specification from psi into bar or kPa before comparing manuals.
• Convert laboratory or engineering values between Pa, kPa, MPa, bar, atm, mmHg, and Torr without chaining several rounded conversions.
• Re-express atmospheric pressure between hPa, kPa, Pa, and atm when comparing weather, aviation, or technical data.
• Prepare a traceable spreadsheet snapshot of a pressure conversion for documentation or review.

How to calculate

1. The calculator opens with a demonstration of 2.24 atm. Its equivalent values are already populated, and Download Excel is immediately available for that example.
2. Replace any one pressure field with your value. Use a period for the decimal separator. Standard grouped numbers such as 101,325 and scientific notation such as 1e6 are accepted; ambiguous decimal-comma text such as 1,5 is rejected rather than silently interpreted.
3. Read the primary Pressure in pascals result, the summary cards, and the full Conversion table. Editing a different unit makes that field the new source and recomputes every equivalent value.
4. Open More conversion options when you need kPa, hPa, MPa, mmHg, or Torr as the editable source.
5. Select Download Excel to create an XLSX workbook from the current validated state. Select Reset to clear the demonstration and every pressure field; after Reset, export stays unavailable until you enter a complete valid value again.

Input guide

Only one pressure field is required at a time: whichever field you edit becomes the source, and the calculator fills the other eight with equivalents. Pressure in bar can serve as that source and accepts a finite decimal pressure in bar; 2.5 is a realistic example. One bar equals 100,000 Pa, so increasing bar increases every converted output linearly. Do not enter the unit text inside the field. Pressure in pounds per square inch can be the source and accepts a finite psi value such as 35; it is useful for U.S. equipment ratings, and the calculator uses the NIST factor of about 6,894.757 Pa per psi. Pressure in atmospheres can be the source and accepts a finite atm value such as 1 or the startup 2.24; one standard atmosphere is exactly 101,325 Pa. A common mistake is treating “atm” as the current local weather pressure rather than the defined standard unit.

Pressure in pascals can be the source and accepts a finite Pa value such as 101325; it is the canonical SI field and can become numerically large for everyday pressures. Pressure in kilopascals accepts kPa such as 220, with 1 kPa = 1,000 Pa. Pressure in hectopascals accepts hPa such as 1013.25; one hPa equals 100 Pa and is numerically equal to one millibar. The National Weather Service glossary confirms the hPa/millibar equivalence in meteorological use. Pressure in megapascals accepts MPa such as 20; this scale is convenient for high-pressure engineering values because 1 MPa = 1,000,000 Pa.

Pressure in millimeters of mercury accepts conventional mmHg such as 760; this calculator uses the conventional factor 133.322387415 Pa per mmHg. Pressure in torr accepts Torr such as 760; Torr is defined as exactly one seven-hundred-sixtieth of a standard atmosphere. mmHg and Torr are very close, but the two definitions are not represented by exactly the same factor here, so high-precision values can differ slightly. All fields accept ordinary decimals, correctly grouped U.S.-style numbers, and scientific notation such as 1e6. Negative finite numbers are also accepted as mathematical conversions, which can be useful for gauge-pressure offsets, but a negative converted value should not be interpreted as a physically valid absolute pressure without context.

Output guide

Pressure in pascals is the primary result and the internal base used for conversion. The summary pills show bar, psi, atm, and Pa equivalents for quick scanning. The result cards repeat Pressure in bar, Pressure in psi, Pressure in atmospheres, and Pressure in kilopascals. Higher or lower values simply represent higher or lower pressure in another unit; zero remains zero in every unit, and a negative source stays negative in every unit.

The Conversion table has three columns. Pressure unit names the unit, Converted value gives the current equivalent, and Pascals per unit shows the factor used to move from that unit into Pa. These are conversion identities, not recommendations or predicted measurements. Display rounding is for readability; the XLSX workbook stores the canonical numeric values used by the model.

Worked example

The startup example uses 2.24 atm. First convert atmospheres to pascals: 2.24 × 101,325 = 226,968 Pa. Then convert pascals to bar by dividing by 100,000: 226,968 ÷ 100,000 = 2.26968 bar. The same canonical pressure is approximately 32.91892526 psi, 226.968 kPa, and 1,702.4 Torr. Those values match the first-open controls, result cards, conversion table, and Excel workbook.

Learn more

For authoritative factors, see NIST's pressure and gas-flow unit conversion table and the NIST Guide to the SI conversion factors. For weather terminology, the National Weather Service explains that one hectopascal equals one millibar.