Speed converter: km/h, mph, m/s and knots
Convert speeds between road, running, ship and aviation units.
How to use this calculator
- Enter the speed.
- Choose the unit to convert from.
- Choose the unit to convert to.
- Read the answer and the table.
Worked examples
Example 1
80 km/h in miles per hour.
You enter
| Value | 80 |
|---|---|
| From | Kilometres per hour (km/h) |
| To | Miles per hour (mph) |
You get
| 80 Kilometres per hour | 49.70969538 Miles per hour |
|---|
Example 2
30 knots in km/h.
You enter
| Value | 30 |
|---|---|
| From | Knots |
| To | Kilometres per hour (km/h) |
You get
| 30 Knots | 55.56 Kilometres per hour |
|---|
How it works
To change km/h to m/s divide by 3.6. A knot is one nautical mile per hour, which is 1.852 km/h.
Speed limits and vehicle displays use km/h in India and mph in the United States and United Kingdom.
Formula
Value in the new unit = value x (m/s per old unit) / (m/s per new unit).
Common questions
Are the conversions exact?
They use the standard defined factors, shown to up to 8 decimal places.
Can I convert between any two units?
Yes, choose any 'from' and 'to' unit; the table shows every unit at once.
Why does km/h to mph not look round?
The two systems were defined separately, so the factor is usually not a round number.
Calculators give estimates for learning and planning. They are not financial, tax, legal or medical advice, and results depend entirely on the numbers you enter. Check rates, limits and rules with an official source or a qualified professional before acting.