Speed Distance Time Calculator: Solving for Any of the Three
Speed, distance and time are linked by one relationship: distance = speed × time. Supply any two values and the third follows — the calculation behind journey planning, running paces, cycling splits and physics homework alike.
The three rearrangements
- Distance = speed × time
- Speed = distance ÷ time
- Time = distance ÷ speed
Keep the units consistent
The single most common error is mixing units. If speed is in km/h, time must be in hours, so 45 minutes is 0.75 rather than 45. Useful conversions: 1 m/s = 3.6 km/h, 1 mph = 1.609 km/h, and 1 knot = 1.852 km/h. Convert everything before you calculate, not afterwards.
Average speed is not the average of speeds
Driving 60 km at 60 km/h and 60 km at 30 km/h takes 1 hour plus 2 hours for 120 km — an average of 40 km/h, not 45. Average speed is always total distance divided by total time, and slower segments dominate because you spend longer in them. The same logic explains why the last slow mile ruins a race average.
Pace for runners and cyclists
Runners work in pace, the inverse of speed — minutes per kilometre or mile. A 5:00/km pace is 12 km/h, and a marathon at that pace takes about 3 hours 31 minutes. Multiply your target pace by the distance to check whether a goal time is realistic before race day.
Key takeaways — Speed Distance Time Calculator
- One formula, three rearrangements — convert units before calculating.
- Average speed = total distance ÷ total time, never the mean of the speeds.
- Pace is the inverse of speed and is easier to run to.