The speed, distance and time triangle
Speed, distance and time are linked by one simple relationship. If you know any two, you can find the third. That is useful for planning a road trip, estimating arrival time, checking a train's average speed, training for a 10K run or solving maths and physics homework. This calculator handles the unit conversions for you and also shows running pace.
How to use the calculator
- Choose what you want to find: time, speed or distance.
- Enter the two known values and choose their units.
- Read the answer, along with the equivalent in other units and the pace per kilometre.
The formulas
Speed = Distance ÷ Time
Distance = Speed × Time
Time = Distance ÷ Speed
A handy memory trick is the triangle with D on top and S and T below: cover the one you want, and the other two show the operation.
Examples
- Travel time: 180 km at an average of 60 km/h takes 180 ÷ 60 = 3 hours.
- Average speed: a 5 km run finished in 30 minutes is 5 ÷ 0.5 = 10 km/h, a pace of 6:00 minutes per km.
- Distance: a train averaging 110 km/h for 2 hours 30 minutes covers 110 × 2.5 = 275 km.
Unit tips
- Convert minutes to hours by dividing by 60: 45 minutes = 0.75 h. The calculator does this automatically.
- km/h to m/s: divide by 3.6. 72 km/h = 20 m/s.
- 1 mile = 1.609 km, so 60 mph ≈ 96.6 km/h.
Average speed is not the average of speeds
If you drive 60 km at 30 km/h and then 60 km at 60 km/h, your average speed is not 45 km/h. The trip takes 2 h + 1 h = 3 h for 120 km, so the true average is 120 ÷ 3 = 40 km/h. Always divide total distance by total time.
Frequently asked questions
What is running pace?
Pace is the time taken per kilometre (or mile), the inverse of speed. Runners use it to plan races.
How much fuel will my trip use?
Use the Fuel Cost Calculator with the same distance.
Does it account for traffic and stops?
No. Use a realistic average speed that includes stops for a better estimate.