Speed, distance and time are tied together by one simple relationship: how far you go equals how fast you go multiplied by how long you go. Knowing any two lets you find the third. This calculator solves for whichever one you need, accepts the units you actually have, and converts the answer into the other common units.
How to use the calculator
- Choose what to solve for: speed, distance or time.
- Enter the two known values. Distance can be in miles, kilometers, meters, feet, yards or nautical miles; speed in mph, km/h, m/s, ft/s or knots.
- Time is entered as hours, minutes and seconds — fill in any combination, such as 0 hours and 45 minutes.
- The tape shows the answer plus conversions. When solving for speed, it also shows your pace per unit of distance.
The formulas
A handy memory aid is a triangle with d on top and s and t on the bottom: cover the one you want, and the other two show whether to multiply (side by side) or divide (one over the other).
The units must agree. If the speed is in miles per hour, distance must be in miles and time in hours. When your units do not match, the calculator converts everything to meters and seconds behind the scenes and converts back.
Worked examples
Time: a 150-mile drive at 60 mph takes 150 ÷ 60 = 2.5 hours = 2 hours 30 minutes.
Speed: a 10 km run in 45 minutes. Convert the time to hours: 45 ÷ 60 = 0.75 h. Speed = 10 ÷ 0.75 = 13.33 km/h (about 8.28 mph), a pace of 4:30 per kilometer.
Distance: 1 hour 30 minutes at 55 mph is 55 × 1.5 = 82.5 miles.
Unit conversions used
| From | To | Multiply by |
|---|---|---|
| mph | km/h | 1.609344 |
| km/h | mph | 0.621371 |
| m/s | km/h | 3.6 |
| knots | mph | 1.150779 |
| ft/s | mph | 0.681818 |
These come from the exact definitions 1 mile = 1,609.344 m, 1 foot = 0.3048 m and 1 nautical mile = 1,852 m, as published by NIST. For other conversions, see the speed converter.
Average speed is not the average of speeds
If you drive 60 miles at 30 mph and the next 60 miles at 60 mph, your average speed is not 45 mph. The first leg takes 2 hours and the second takes 1 hour, so you cover 120 miles in 3 hours: an average of 40 mph. Always divide the total distance by the total time. The average velocity calculator handles trips with several legs, and runners can plan splits with the pace calculator.
Frequently asked questions
What is the formula for speed, distance and time?
Distance = speed × time. Rearranged, speed = distance ÷ time and time = distance ÷ speed. The units must match: miles with miles per hour, kilometers with kilometers per hour.
How long does it take to drive 150 miles at 60 mph?
Time = 150 ÷ 60 = 2.5 hours, which is 2 hours 30 minutes. The calculator shows the same time as decimal hours, minutes, seconds and h:mm:ss.
How do I convert 0.75 hours into minutes?
Multiply the decimal part by 60: 0.75 × 60 = 45 minutes. In the other direction, divide minutes by 60, so 45 minutes is 0.75 hours. The calculator does this conversion for you in both directions.
Is the result my actual travel time?
It is the time at a constant speed. Real trips include stops, traffic and speed changes, so use your expected average speed rather than the speed limit for a realistic estimate.