Speed Converter
Convert speeds between m/s, km/h, mph, knots, ft/s, Mach and km/s with worked steps and a table of every result.
Speed Converter — input your values
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Did you know?
The speed converter handles the speed units you meet on roads, in aviation, at sea and in physics: kilometers per hour, miles per hour, meters per second, feet per second, knots, Mach and kilometers per second.
Recommendation
Rough mental math: 1 mph ≈ 1.61 km/h, and to go the other way divide by 1.61.
Also worth knowing
A knot is 1.852 km/h exactly — aviation and maritime speeds are always quoted in knots.
What does this conversion calculator do?
The speed converter handles the speed units you meet on roads, in aviation, at sea and in physics: kilometers per hour, miles per hour, meters per second, feet per second, knots, Mach and kilometers per second.
Every speed is converted through meters per second as the reference base. A knot is one nautical mile per hour, Mach compares a speed to the speed of sound, and the converter includes both in the same table for easy comparison.
Formula and variables
Mach is approximate: the speed of sound varies with altitude and temperature; 340.29 m/s is the value at sea level and 15 °C.
| Symbol | Meaning |
|---|---|
| factor(from) | How many m/s one 'from' unit equals |
| factor(to) | How many m/s one 'to' unit equals |
Worked example
Convert 60 miles per hour to kilometers per hour.
- 60 mph × 0.44704 = 26.8224 m/s.
- 26.8224 m/s ÷ 0.2777777778 = 96.56064 km/h.
Answer: 60 mph ≈ 96.56 km/h.
Tips and common mistakes
Tips
- Rough mental math: 1 mph ≈ 1.61 km/h, and to go the other way divide by 1.61.
- A knot is 1.852 km/h exactly — aviation and maritime speeds are always quoted in knots.
- For weather and physics, use m/s: 10 m/s is a strong breeze, about 36 km/h or 22 mph.
- Mach 1 is not constant — aircraft hit Mach 1 faster at high altitude because the speed of sound drops with temperature.
Common mistakes to avoid
- Treating knots and mph as similar — a knot is about 15% faster than 1 mph.
- Forgetting that km/h and m/s differ by a factor of 3.6, not 100.
- Using sea-level Mach values for high-altitude aircraft where the speed of sound is lower.
Speed Converter — frequently asked questions
How do I convert km/h to mph?
Divide km/h by 1.609344. For example, 100 km/h ÷ 1.609344 ≈ 62.14 mph.
How many mph is 1 knot?
One knot equals 1.150779 mph, or 1.852 km/h. Knots are standard in aviation and maritime navigation.
What does Mach 1 mean?
Mach 1 is the speed of sound, about 340.29 m/s (1,225 km/h) at sea level. It varies with temperature and altitude.
How many m/s is 1 km/h?
One km/h equals 1/3.6 ≈ 0.27778 m/s. So 90 km/h is 25 m/s — a useful safety benchmark for driving.
Is the speed of sound constant?
No — it depends on temperature: at 15 °C it is about 340 m/s, and it drops to roughly 300 m/s at −50 °C, such as at cruising altitude.
How fast is the speed of light in km/s?
Approximately 299,792 km/s — this is well beyond the units in the table but is the absolute speed limit of the universe.
How this calculator works
Speed Converter uses the formula shown above (result = value × factor(from) ÷ factor(to)) and computes the result instantly in your browser — no data leaves your device.