How it works
Average lap speed is the track length divided by the lap time. The calculator converts the lap time to seconds, divides, and multiplies by 3,600 to give miles or kilometres per hour. For the reverse, it divides the length by your target speed. It converts between units using the international definition of the mile, 1.609344 kilometres.
A published example to check it against: Guinness World Records lists Max Verstappen's qualifying lap for the 2025 Italian Grand Prix at Monza (6 September 2025) as 1 minute 18.792 seconds, at an average of 264.682 km/h (164.466 mph), and Formula 1 gives the Monza circuit length as 5.793 km. Entering 5.793 kilometres and 1:18.792 here gives 264.68 km/h (164.47 mph), the same figures rounded to two decimal places.
The result is only as good as the track length you enter. Use the length the circuit or series publishes for the layout you drove. That published figure is a reference distance, so the average speed it gives is a reference figure too. An average speed says nothing about where on the lap time was gained or lost; for that, see data and video.