What is being measured?
Pressure is force per area. Unit scaling cannot change a gauge-pressure reading into an absolute-pressure reading without the reference pressure.
Atmospheres are standard atmospheres. Mercury-column factors use the conventional 0 °C definition; torr is 1/760 of a standard atmosphere.
Meaning of atm
atmospheres uses the symbol atm in this library and measures pressure. Under the stated reference convention, 1 atm = approximately 101325 Pa. This equivalence changes how a known value is written. It does not increase measurement accuracy or establish whether a measurement is appropriate to a real application.
Conversion method
Multiply the value by the source factor (101325), then divide by the target factor (1). The factor ratio expresses the same pressure measurement in the other unit.
Worked example
For a known value of 10 atm, the reference conversion gives 1013250 Pa. Converting that result back gives approximately 10 atm. This reverse check helps catch a reversed factor, but matching round-trip arithmetic alone does not independently verify a source definition.
Common reference values
| Input (atm) | Reference equivalent (Pa) |
|---|---|
| 1 | 101325 |
| 5 | 506625 |
| 10 | 1013250 |
| 25 | 2533125 |
| 50 | 5066250 |
| 100 | 10132500 |
Compare one atm with other units
| Target unit | Equivalent of 1 atm | Definition guide |
|---|---|---|
| Pascals (Pa) | 101325 | Read definition |
| Kilopascals (kPa) | 101.325 | Read definition |
| Bars (bar) | 1.01325 | Read definition |
| Pounds per square inch (psi) | 14.6959487755 | Read definition |
| megapascals (MPa) | 0.101325 | Read definition |
| millibar (mbar) | 1013.25 | Read definition |
| Conventional millimetres of mercury (mmHg (0 °C)) | 759.999891726 | Read definition |
| Conventional inches of mercury (inHg (0 °C)) | 29.9212555797 | Read definition |
Precision and common mistakes
- Keep the source and target quantity consistent. A matching symbol is not enough to establish a compatible definition.
- Record the original measurement precision. Showing twelve significant digits in a table does not make a rounded input more precise.
- Check symbol capitalization, prefixes and any regional convention in the source. Use the displayed unit definition rather than a similarly named unit.
- Factors involving repeating fractions or π use finite numerical precision. Round the final answer to the precision justified by your input.
Use a working converter
- Pressure converter
- Atmospheres to Pascals converter
- Atmospheres to Kilopascals converter
- Atmospheres to megapascals converter
- Atmospheres to Bars converter
- Atmospheres to millibar converter
Source and verification scope
Examples and tables are computed from the versioned unit definitions used by the linked converters. The source access dates appear below. Computandum is independent of the cited organizations; a citation does not mean that a publisher endorses this page or an actual project.
Sources
- NIST / BIPM: NIST: unit conversion factors ↗ · 2026-10-08