Speed Calculator
Find average speed, distance, or travel time from any two of the three, in mph and km/h.
🚗 What is the Speed Calculator?
The speed calculator works with the single most useful relationship in travel: speed equals distance divided by time. Because that one equation can be rearranged, the calculator solves any of the three quantities when you know the other two. Choose a tab to find average speed, distance, or travel time, and it returns the answer in both imperial and metric units.
People use it constantly without always naming it. A driver planning a trip wants to know how long 300 miles will take at an average of 50 mph. A cyclist wants their average speed over a measured ride. A student checks a physics homework answer. A delivery planner works out how far a van can cover in a shift. All three questions are the same equation viewed from a different angle, which is exactly what the three tabs provide.
The key idea to remember is that this is average speed, not instantaneous speed. Average speed spreads the whole journey, including stops and slow sections, across the total time, which is why a trip where you cruised at 70 mph on the motorway can still average 55 mph once towns and junctions are counted. It is also why you should never average the speeds of separate segments directly: add the distances and the times, then divide.
This tool is useful because it removes the mental arithmetic and the unit juggling. Enter any two values, pick miles or kilometres, and get the third instantly in mph and km/h, with time shown in tidy hours and minutes and the working laid out so the method is clear.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - Average speed of a 150-mile drive
Example 2 - Distance at 60 mph for 3h 15m
Example 3 - Time for 300 miles at 50 mph
❓ Frequently Asked Questions
🔗 Related Calculators
How do you calculate average speed?
Divide the total distance by the total time. If you travel 150 miles in 2 hours 30 minutes, first convert the time to 2.5 hours, then 150 / 2.5 = 60 mph. Average speed uses the whole trip, so stops and slow sections are already included in the time.
How do I find distance from speed and time?
Multiply speed by time. At 60 mph for 3 hours 15 minutes (3.25 hours), distance = 60 x 3.25 = 195 miles. Make sure the time is in hours, converting minutes by dividing by 60, so 15 minutes becomes 0.25 hours.
How do I calculate travel time from distance and speed?
Divide distance by speed. A 300-mile drive at an average of 50 mph takes 300 / 50 = 6 hours. If the result is not a whole number, multiply the decimal part by 60 to get the minutes; for example 6.5 hours is 6 hours 30 minutes.
What is the difference between average and instantaneous speed?
Average speed is total distance divided by total time for a journey, while instantaneous speed is how fast you are going at a single moment, like the reading on a speedometer. This calculator computes average speed, which is what you need for trip planning and fuel estimates.
How do I convert mph to km/h?
Multiply miles per hour by 1.609 to get km/h, or divide km/h by 1.609 to get mph. So 60 mph is about 96.6 km/h. This calculator shows both units at once, so you do not need to convert manually.
Can I use this for running or cycling pace?
Yes. Enter the distance and the time and it returns your average speed in mph and km/h. For running you may prefer pace in minutes per mile or per kilometre, which is the inverse of speed, but the same distance and time inputs give you the speed directly.
How do I average speed over a trip with different segments?
Do not average the segment speeds directly, because time spent at each speed matters. Instead add up all the distances and all the times, then divide total distance by total time. That gives the true average speed for the whole journey.
Why is my average speed lower than the speed I drove?
Average speed includes every stop, slowdown, and traffic delay, spread across the whole trip time. Even short stops pull the average down. A drive where you cruised at 70 mph on the highway can easily average 55 mph once junctions, towns, and a coffee stop are counted.