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Speed Unit Converter
Convert speed between mph, km/h, m/s, ft/s, and knots. Updates instantly as you type.
1) Enter a speed
Two-way · updates as you type
Tip: You can type into either box. Changing units recalculates automatically.
2) Multi-unit outputs
Same input, all units
Reference: 1 mph = 1.609344 km/h. Knots are used for marine/aviation (1 kt = 1 nautical mile per hour).
Explainer
How the conversion works
| Unit | Meaning | Exact base conversion |
|---|---|---|
| mph | Miles per hour | 1 mph = 0.44704 m/s |
| km/h | Kilometers per hour | 1 km/h = 0.277777… m/s |
| m/s | Meters per second | Base unit used internally |
| ft/s | Feet per second | 1 ft/s = 0.3048 m/s |
| knots | Nautical miles per hour | 1 kt = 0.514444… m/s |
The converter converts From → m/s → To using exact factors (where defined).
Examples
Common conversions
| Example | Result | Where you see it |
|---|---|---|
| 65 mph → km/h | ~104.6 km/h | US highway speeds |
| 100 km/h → mph | ~62.1 mph | Many countries’ highways |
| 10 m/s → mph | ~22.4 mph | Wind / physics |
| 20 knots → mph | ~23.0 mph | Boats / aviation |
Quick reference tables
Handy checkpoints
mph → km/h
| mph | km/h |
|---|---|
| 10 | 16.09 |
| 25 | 40.23 |
| 45 | 72.42 |
| 65 | 104.61 |
| 75 | 120.70 |
km/h → mph
| km/h | mph |
|---|---|
| 30 | 18.64 |
| 50 | 31.07 |
| 80 | 49.71 |
| 100 | 62.14 |
| 120 | 74.56 |
Values are rounded to 2 decimals. Your calculator above gives full precision.
FAQ
Short answers
Which unit should I use? Use mph in the US, km/h in most other countries. m/s is common in physics.
What is a knot? One nautical mile per hour (used in marine/aviation).
Why do my values differ slightly from road signs? Rounding and local conventions can differ; this tool uses standard conversion factors.
Does this account for wind, slopes, or speedometer error? No — it’s a pure unit conversion.
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