Speed Calculator
Calculate average speed from the distance traveled and time taken.
How this calculator works
Average speed is simply total distance divided by total time — it doesn't account for variations in speed during the trip.
Result shown in both mph and km/h.
Average speed vs. instantaneous speed
This calculator computes average speed over an entire trip, which differs from instantaneous speed (your speedometer reading at any given moment). A trip with stops, traffic, or speed variation will show a lower average speed than the peak speed reached at any point.
This distinction matters for trip planning — knowing your required average speed to arrive on time is more useful than just knowing your vehicle's top speed capability.
A worked example
Driving 240 miles in 4 hours: average speed equals 240 divided by 4, or 60 mph, about 96.6 km/h.
For a runner covering 6.2 miles (10K) in 55 minutes (0.917 hours): average speed is approximately 6.76 mph, about 10.87 km/h — useful for comparing pace across different distance units.
Average speed vs. instantaneous speed
This calculator computes average speed over an entire trip — total distance divided by total time — which is different from instantaneous speed (what a speedometer shows at any given moment). A trip with stops or varying speeds will show a lower average speed than the peak speed reached during the fastest segment.
This distinction matters for trip planning — knowing your average speed (including stops) is more useful for estimating total travel time than knowing your top cruising speed alone.
Frequently asked questions
Does this show instantaneous or average speed?
Average speed over the whole distance and time entered — it won't reflect variations like stops or speed changes during the trip.
Why is my average speed lower than the speed limit I drove at?
Stops, traffic, and slower sections all pull down the average, even if you spent much of the trip at or near the speed limit — average speed accounts for the entire trip time, including any slow segments.
How do I calculate required speed to arrive by a certain time?
Divide the remaining distance by the remaining time until your target arrival — this calculator can help by rearranging: if you know distance and desired time, the result shows the average speed needed.
Why is my average speed lower than my top speed?
Average speed accounts for the entire trip, including any stops, slowdowns, or traffic — it will always be lower than or equal to your peak instantaneous speed during the fastest portion of the trip.