Speed Calculator guide
Speed Calculator: Speed, Distance and Time
Use our speed calculator to work out average speed, distance or time, in mph, km/h, m/s or knots.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
Speed, distance and time are linked by one simple formula. Our Speed Calculator finds whichever one you need.
How to use the calculator (Speed Calculator)
- Choose what to find: speed, distance or time.
- Enter the other two values and choose your units.
The formula
Speed = distance ÷ time
Rearranged:
- Distance = speed × time
- Time = distance ÷ speed
A handy way to remember it is the triangle: D at the top, S and T at the bottom.
Speed conversions
| From | To | Multiply by |
|---|---|---|
| mph | km/h | 1.609 |
| km/h | mph | 0.621 |
| m/s | km/h | 3.6 |
| knots | mph | 1.151 |
A worked example
With the calculator's default settings, 120 miles in 2 hours is an average speed of 60 mph, or 96.6 km/h.
Frequently asked questions
Is average speed the same as average of speeds?
No. If you drive 60 miles at 30 mph and 60 miles at 60 mph, your average speed is 40 mph, not 45, because you spent longer at the slower speed.
What's a knot?
One nautical mile (1,852m) per hour, used at sea and in aviation.
What are the UK speed limits?
30 mph in built-up areas, 60 mph on single carriageways and 70 mph on dual carriageways and motorways, for cars, unless signs say otherwise.
For running pace, use our Pace Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.