Physics, units and measurement
Scientific unit converter with SI prefixes
Convert length, mass, volume, pressure, energy, temperature, amount and concentration, with every SI prefix from quecto to quetta and exact factors.
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Result
- 1.000 atm =
- 101.325 kPa
- Rounded to your 4 significant figures
- 101.3 kPa
Working
- 1.000 atm × (101325 Pa per atm) ÷ (1000 Pa per kPa)
| Unit | Value | Name | Definition |
|---|---|---|---|
| MPa | 0.101325 | megapascal | exact |
| kPa | 101.325 | kilopascal | exact |
| Pa | 101325 | pascal | exact |
| bar | 1.01325 | bar | exact |
| mbar | 1013.25 | millibar | exact |
| atm | 1 | standard atmosphere | exact |
| Torr | 760 | torr | exact |
| mmHg | 759.9998917 | millimetre of mercury (conventional) | exact |
| psi | 14.69594878 | pound-force per square inch | exact |
| inHg | 29.9212524 | inch of mercury (conventional) | exact |
| cmH₂O | 1033.227453 | centimetre of water (conventional) | exact |
- Results show up to 10 significant figures with trailing zeros dropped; round them to the precision of your measurement.
Method and limits
Choose a unit and, for SI units, a prefix on each side. The answer and a table of the same value in every unit of that quantity update as you type. Prefixes attach to the first symbol of a compound unit: “milli” with g/L gives mg/L.
value(to) = value(from) × factor(from) ÷ factor(to) (temperatures: via kelvin, T(K) = t(°C) + 273.15)
Every factor converts to the coherent SI unit. Most are exact by definition: the inch is 0.0254 m, the pound 0.453 592 37 kg, the standard atmosphere 101 325 Pa, the thermochemical calorie 4.184 J, the electronvolt e × 1 J/C with e = 1.602 176 634 × 10⁻¹⁹ C. The dalton and the hartree are measured CODATA 2022 constants and are marked as such. Molar energies divide by the exact Avogadro constant; wavenumber, frequency and temperature use E = hcν̃, E = hν and E = kT with exact h, c and k.
SI prefixes
| Prefix | Symbol | Factor |
|---|---|---|
| quetta | Q | 10³⁰ |
| ronna | R | 10²⁷ |
| yotta | Y | 10²⁴ |
| zetta | Z | 10²¹ |
| exa | E | 10¹⁸ |
| peta | P | 10¹⁵ |
| tera | T | 10¹² |
| giga | G | 10⁹ |
| mega | M | 10⁶ |
| kilo | k | 10³ |
| hecto | h | 10² |
| deca | da | 10¹ |
| deci | d | 10⁻¹ |
| centi | c | 10⁻² |
| milli | m | 10⁻³ |
| micro | µ | 10⁻⁶ |
| nano | n | 10⁻⁹ |
| pico | p | 10⁻¹² |
| femto | f | 10⁻¹⁵ |
| atto | a | 10⁻¹⁸ |
| zepto | z | 10⁻²¹ |
| yocto | y | 10⁻²⁴ |
| ronto | r | 10⁻²⁷ |
| quecto | q | 10⁻³⁰ |
Limits
- Concentrations in ppm and ppb are mass per volume of a dilute aqueous solution (1 ppm = 1 mg/L), which assumes a density of 1 g/mL; for other solutions they need the density.
- mmHg and inHg are the conventional values (mercury at 0 °C under standard gravity); real columns depend on temperature.
- Results show up to 10 significant figures; round them to the precision of your measurement (the second line does this for you).
Worked example
1 atm = 101 325 Pa exactly, so 1 atm = 101.325 kPa = 1.01325 bar = 760 Torr = 14.69595 psi. 25 °C = 298.15 K = 77 °F. 1 eV per particle = 96.485 33 kJ/mol = 8065.544 cm⁻¹.
References
Related tools
- Physical constants (CODATA 2022)All 355 CODATA 2022 fundamental physical constants from NIST, searchable, with standard uncertainties, exact values marked and copyable rows.
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