Average Lap Speed Calculator

Speed in mph is the track length in miles divided by the lap time expressed in hours, and lap time in hours is the lap seconds divided by 3600. A kilometre length is first divided by 1.609344 to convert it to miles, then the same formula runs.

The mph figure is multiplied by 1.609344, the exact number of kilometres in a mile. Both numbers appear side by side so you never have to convert by hand, and the km/h card matches a kilometre track length exactly.

No. This is the mean speed over the entire lap, so it folds in braking zones, apex speeds and corner exits. Your top speed on the longest straight is always higher than the lap average.

Enter the time as a decimal number of seconds, not as minutes and seconds. A one minute fifteen second lap is 75, a one minute thirty lap is 90, and a lap of 88.4 seconds is entered as 88.4.

Yes. Switch the unit dropdown to km and type the lap distance in kilometres. The tool converts it to miles internally for the mph card while the km/h card reflects the kilometre distance directly.

Both fields must hold a positive number. If either is empty, zero or negative, an amber note appears asking for the track length and lap time, and no speed is shown until valid values are present.

Each speed is shown to two decimal places using your locale formatting. The underlying maths keeps full precision, so rounding only happens at display time, not partway through the calculation.

No estimating. It treats the lap length you enter as the exact distance covered in one lap, so accuracy depends on measuring your track length correctly rather than on any built-in assumptions.

No. The calculation runs entirely in your browser with no server call, so your lap times and track details never leave your device.

Yes, use the lap time calculator instead. It takes a track length and a target average speed and returns the lap time you would need, which is the inverse of this tool.