Speed, Distance & Time Calculator
Solve for speed, distance, or time when you know the other two — pick which one to find.
The formula
Speed = Distance ÷ Time. Rearranged: Distance = Speed × Time, and Time = Distance ÷ Speed.
Worked example
Travelling 150 km in 3 hours gives a speed of 150 ÷ 3 = 50 km/h.
Solving for distance and for time
Driving at 80 km/h for 2.5 hours covers 80 × 2.5 = 200 km. To find a travel time, 420 km at 90 km/h takes 420 ÷ 90 = 4.67 hours, which is 4 hours and 40 minutes. The time result is always in decimal hours, so multiply the fraction by 60 to get minutes: 0.67 × 60 is about 40.
Average speed is not moving speed
Covering 300 km in 4 hours is an average of 75 km/h. If the same trip includes a one-hour stop, it takes 5 hours and the average falls to 60 km/h, although the car never slowed down while moving. Divide by the full elapsed time to get the average over the trip, and by driving time only to get the moving speed.
Averages of two legs do not combine by simple averaging. Driving 120 km at 60 km/h takes 2 hours and 120 km at 90 km/h takes 1 hour 20 minutes, so 240 km takes 3.333 hours. Entering 240 km and 3.3333 hours gives 72 km/h, not 75.
Units and what is checked
- The labels are fixed to km, hours and km/h. To use miles, enter miles and mph consistently; one mile is 1.609344 km.
- To convert km/h to meters per second, divide by 3.6.
- Enter time as decimal hours: 2 hours 30 minutes is 2.5 and 45 minutes is 0.75.
- Speed mode needs a time above zero, and time mode needs a speed above zero. In every mode a negative distance, time or speed shows an error asking for positive values.
Frequently asked questions
Can I use different units like miles or minutes?
The fields and result labels are fixed to kilometers, hours and km/h. If you enter miles and miles per hour the arithmetic is still right, but the label will say km. Minutes must be converted to hours first, for example 45 minutes is 0.75.
Does this account for acceleration?
No, this calculates average speed over a distance and time, assuming constant speed. It doesn't model acceleration or changing speed during the journey.
How do I enter 2 hours and 30 minutes?
Convert the minutes to a fraction of an hour and add them: 2 hours 30 minutes is 2.5, and 1 hour 15 minutes is 1.25.
Why does my average speed differ from what the speedometer showed?
The speedometer shows moving speed at one instant. The calculator divides total distance by total elapsed time, so stops, traffic and slow sections lower the average below your cruising speed.
Can I use this for a journey with several legs?
Yes, but add the distances together and add the times together, then solve for speed. Averaging the leg speeds gives the wrong answer unless every leg took the same time.