The speed of light in miles per hour, km/h and other units
The speed of light in vacuum is exactly 299 792 458 metres per second by definition, and the mile, foot and nautical mile are also defined exactly in metres, so every value below is exact; long ones are rounded only for display.
= 299 792 458 m s−1 about this constant →
| Unit | Value | |
|---|---|---|
| km/s kilometres per second | 299 792.458 | exact |
| km/h kilometres per hour | 1 079 252 848.8 | exact |
| mph miles per hour | 670 616 629.384 | exact |
| mi/s miles per second | 186 282.397 051 | exact |
| ft/s feet per second | 983 571 056.43 | exact |
| ft/ns feet per nanosecond | 0.983 571 056 43 | exact |
| kn knots | 582 749 918.359 | exact |
| au/d astronomical units per day | 173.144 632 674 | exact |
| ly/yr light-years per Julian year | 1 | exact |
How it is computed: 299 792 458 m/s × 3600 s/h ÷ 1609.344 m/mi = 670 616 629.384.
All values computed from the CODATA 2022 value and unit definitions (SI Brochure, NIST SP 811). Exact values are rounded only for display. Checks.
Other conversions
- Gravitational constant G in CGS and other units
- Planck constant in eV·s and other units
- Reduced Planck constant ħ in eV·s, MeV·fm and other units
- Boltzmann constant in eV/K and other units
- Gas constant R in L·atm/(mol·K), cal/(mol·K) and other units
- Electron mass in MeV/c², grams and daltons
- Elementary charge in statcoulombs (esu) and other units
- Standard gravity in ft/s², m/s² and other units
- Avogadro constant per pound-mole and other units