Kilometers per second to times the speed of light
Type a value in kilometers per second to see it in times the speed of light straight away, or type in the second box to convert back.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the kilometers per second box.
- Read the result in times the speed of light as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
c = km/s × 0.000003335640952
Multiply the value in kilometers per second by 0.000003335640952 to get times the speed of light.
Example
To convert 25 km/s to times the speed of light: 25 × 0.000003335640952 = 0.000083391 c.
Conversion table
| Kilometers per second (km/s) | Times the speed of light (c) |
|---|---|
| 1 | 0.00000333564 |
| 2 | 0.00000667128 |
| 3 | 0.0000100069 |
| 5 | 0.0000166782 |
| 10 | 0.0000333564 |
| 20 | 0.0000667128 |
| 25 | 0.000083391 |
| 50 | 0.000166782 |
| 100 | 0.000333564 |
| 250 | 0.00083391 |
| 500 | 0.00166782 |
| 1,000 | 0.00333564 |
About the units
- Kilometer per second
- Covering 1000 meters in one second. It is used for satellites, rockets and astronomical objects.
- Speed of light
- The speed of light in vacuum, fixed by the SI definition at exactly 299,792,458 m/s.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many times the speed of light are in one kilometer per second?
1 km/s = 0.00000333564 c exactly.
How do I convert kilometers per second to times the speed of light?
Use c = km/s × 0.000003335640952. For example, 25 km/s = 0.000083391 c.
How many kilometers per second are in one speed of light?
1 c = 299,792 km/s.
How do I convert km/h to m/s in my head?
Divide by 3.6, because an hour is 3600 seconds and a kilometer is 1000 meters. For example 72 km/h is 20 m/s; multiply by 3.6 to go back.
Why do Mach values differ between sources?
The speed of sound depends on air temperature. We use 340.294 m/s at sea level and 15 °C; at 11 km altitude it is about 295 m/s, so Mach 1 is slower there.