Speed Calculator

How to use the speed calculator

1. Choose what you want to find: Speed, Distance or Time.
2. Enter the distance and pick its unit (miles, kilometers or meters) when you are solving for speed or time.
3. Enter the time as hours, minutes and seconds when you are solving for speed or distance. Seconds can have decimals, such as 9.58.
4. Enter the speed and pick mph, km/h or m/s when you are solving for distance or time.
5. Read the results: speed in km/h, mph and m/s, distance in kilometers and miles, and the time as h:mm:ss.

Speed, distance and time formulas

Average speed is the distance traveled divided by the time it took. The other two formulas rearrange the same relationship:

• Speed = distance ÷ time
• Distance = speed × time
• Time = distance ÷ speed

The calculator converts everything to meters and seconds first, then back to each unit, using exact definitions:

• 1 mile = 1,609.344 m, so 1 mph = 0.44704 m/s
• 1 km/h = 1,000 m ÷ 3,600 s, so to go from m/s to km/h you multiply by 3.6

Speeds are shown with two decimals, distances with three and time rounded to the nearest second.

Examples

150 miles in 2 hours 30 minutes

Average speed is 60.00 mph, which is 96.56 km/h or 26.82 m/s.

How long is a 240-mile drive at 70 mph?

In Time mode, you get 3:25:43 of driving, before any stops for fuel or food.

How far do you get in 3 hours 15 minutes at 65 mph?

In Distance mode, 211.250 miles, or 339.974 km.

Usain Bolt's 100 m world record

Bolt ran 9.58 seconds at the 2009 World Championships in Berlin. Enter 100 m and 9.58 s: his average speed was 10.44 m/s, 37.58 km/h or 23.35 mph. The time line shows 0:00:10 because it rounds to whole seconds, but the speed uses 9.58. His top speed during the race was higher, since he started from zero.

Average speed vs. instantaneous speed

The result is an average: total distance over total time. Your speedometer shows instantaneous speed, which changes from moment to moment. A trip that averages 55 mph may include stretches at 75 mph and minutes stopped in traffic.

For trip planning, include stops in the time, or add them afterward. Speed limits are a ceiling, not an average, so real averages on a road trip usually come out lower than the posted limit.

In physics, speed is a scalar: it has size but no direction. Velocity also includes direction. If you drive to a store and back, your average speed is positive, but your average velocity for the round trip is zero because you end where you started. This calculator works with speed, the quantity that matters for travel times.