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
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.