Pressure Converter

The pascal (Pa) is the SI unit of pressure, defined as one newton per square metre (N/m²). The kilopascal (kPa = 1,000 Pa) and megapascal (MPa) are the practical engineering units. Standard atmospheric pressure is defined as exactly 101,325 Pa (1 atm). The bar (100,000 Pa) is close to 1 atm and widely used in meteorology and the petroleum industry. The millimetre of mercury (mmHg) remains common for blood pressure and is approximately 133.322 Pa. The torr is defined as exactly 1/760 of a standard atmosphere. The two units are very close in value but their definitions differ.

All conversions in this category are computed relative to a single base unit (Pascal) using factors sourced from NIST Special Publication 811 and the BIPM SI Brochure. A shared reference unit keeps the conversion relationships consistent. Converting directly from the original measurement avoids the rounding differences that can accumulate when displayed intermediate results are entered again.

This calculator supports 10 units, including Pascal, Kilopascal, Megapascal, Bar, Millibar. Choose the unit shown in your source measurement, then the unit needed for your result.

Units may have alternate spellings or abbreviations. You can search using these names too. Examples include Pascal (Pa, also written as pascals or pa), or Kilopascal (kPa, also written as kilopascals or kpa), or Megapascal (MPa, also written as megapascals or mpa).

All pressure conversions within the SI family are purely multiplicative: you multiply the source value by a fixed conversion factor derived from the ratio of the two unit definitions. Imperial-to-metric conversions use the exact defined equivalences (e.g., 1 inch = 25.4 mm exactly) rather than approximations.

When precision matters, avoid rounding intermediate calculations. The displayed factors and results are rounded for readability, usually to ten significant digits; very large or small values use scientific notation. Use the original measurement for each conversion and round the final answer to match the accuracy of that measurement.

Keep the unit alongside each pressure value when you copy or share it. Check that the source and target units match your task. If two units have similar names, read their definitions before selecting one.

For a second check, use the worked example and formula on the conversion page. Start from your original value rather than a rounded result from another calculator. If you need to report a specific number of decimal places, round once at the end.