Kilometers per hour to kilometers per second
Type a value in kilometers per hour to see it in kilometers per second 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 hour box.
- Read the result in kilometers per second as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
km/s = km/h × 0.0002777777778
Multiply the value in kilometers per hour by 0.0002777777778 to get kilometers per second.
Example
To convert 25 km/h to kilometers per second: 25 × 0.0002777777778 = 0.00694444 km/s.
Conversion table
| Kilometers per hour (km/h) | Kilometers per second (km/s) |
|---|---|
| 1 | 0.000277778 |
| 2 | 0.000555556 |
| 3 | 0.000833333 |
| 5 | 0.00138889 |
| 10 | 0.00277778 |
| 20 | 0.00555556 |
| 25 | 0.00694444 |
| 50 | 0.0138889 |
| 100 | 0.0277778 |
| 250 | 0.0694444 |
| 500 | 0.138889 |
| 1,000 | 0.277778 |
About the units
- Kilometer per hour
- Covering 1000 meters in 3600 seconds, so 1 km/h is exactly 1/3.6 m/s. It is the unit on road signs and car speedometers in most countries.
- Kilometer per second
- Covering 1000 meters in one second. It is used for satellites, rockets and astronomical objects.
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 kilometers per second are in one kilometer per hour?
1 km/h = 0.000277778 km/s exactly.
How do I convert kilometers per hour to kilometers per second?
Use km/s = km/h × 0.0002777777778. For example, 25 km/h = 0.00694444 km/s.
How many kilometers per hour are in one kilometer per second?
1 km/s = 3,600 km/h.
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.