Speed converter
Convert miles per hour, kilometres per hour, metres per second and knots. Useful for UK road speeds, travel, running, cycling, aviation and marine speed checks.
Speed converter calculator
Enter a speed, choose the unit you have and choose the unit you want. The calculator converts through metres per second and shows the factor used.
Popular speed conversions
Use these quick buttons for common UK and travel conversions.
How speed conversion works
Most speed conversions can be handled by converting the starting speed into metres per second, then converting that base value into the target unit.
metres per second = original speed × m/s value of original unit
converted speed = metres per second ÷ m/s value of target unitFor example, 1 mph is about 0.44704 m/s. To convert mph to km/h, multiply by 1.609344.
Common speed conversion factors
| Conversion | Factor | Example |
|---|---|---|
| mph to km/h | × 1.609344 | 70 mph ≈ 112.65 km/h |
| km/h to mph | ÷ 1.609344 | 100 km/h ≈ 62.14 mph |
| m/s to km/h | × 3.6 | 10 m/s = 36 km/h |
| km/h to m/s | ÷ 3.6 | 36 km/h = 10 m/s |
| knots to mph | × 1.150779 | 10 knots ≈ 11.51 mph |
| mph to knots | ÷ 1.150779 | 20 mph ≈ 17.38 knots |
UK speed notes
In the UK, road signs and speed limits are normally shown in miles per hour. Kilometres per hour are more common in many other countries, while metres per second appears in technical, weather and science contexts.
- mph: common for UK roads, driving and car-related calculations.
- km/h: common for international road speeds and travel comparisons.
- m/s: useful for physics, engineering, wind speed and technical calculations.
- knots: commonly used in marine and aviation contexts.
Use the drive time calculator for distance, speed and travel-time estimates.
Rounding speed conversions
For everyday comparisons, one or two decimal places is usually enough. For driving, road signs and journey estimates, whole numbers are often easier to read.
Speed converter FAQs
How do you convert mph to km/h?
Multiply miles per hour by 1.609344 to convert to kilometres per hour.
How do you convert km/h to mph?
Divide kilometres per hour by 1.609344 to convert to miles per hour.
How many km/h is 70 mph?
70 mph is about 112.65 km/h.
What is a knot?
A knot is a speed unit used mainly in marine and aviation contexts. One knot is one nautical mile per hour, which is about 1.15078 mph.