Calculation methods
The formulas, worked examples, assumptions and limits behind every tool.
Pace calculator ↗
Pace (seconds/km) = elapsed seconds ÷ distance in km. Speed (km/h) = distance ÷ hours.
Example: 10 km in 50:00 is 5:00 per km, about 8:03 per mile and 12 km/h.
Enter elapsed time including stops if you want an elapsed average. Choose moving time only when that is the metric you intend to calculate.
Finish time ↗
Finish time = distance in km × pace in seconds per km. One mile = 1.609344 km.
Example: 42.195 km at 5:30/km takes 3:52:04.35, displayed as 3:52:04 after rounding to a second.
This is a constant-pace projection, not a prediction of fitness or race performance. The pace input is always minutes and seconds per kilometre, even when the distance is entered in miles.
Race splits ↗
Cumulative time at distance x = target time × x ÷ full distance. Partial final splits use the same pace.
Example: A 21.0975 km half-marathon in 1:45:00 averages about 4:59/km. A 1 km card has 22 rows; the last is 0.0975 km.
Times are calculated at full precision, then rounded for display; adjacent rounded split values may differ by one second. This is an even-pace plan and does not model elevation, stops or negative splits. Maximum 1,000 segments.
Speed converter ↗
Seconds per km = 3,600 ÷ km/h. A 400 m lap takes seconds per km × 0.4.
Example: 12 km/h = 5:00/km = about 7.456 mph. A 400 m lap takes exactly 2:00.
All conversions assume a constant average speed. The 400 m result is for an actual 400 m distance; outer track lanes have different distances unless the start positions are staggered.
Units and numerical limits
Conversions use 1 inch = 2.54 cm, 1 mile = 1.609344 km, and 1 avoirdupois ounce = 28.349523125 g. Empty, non-finite, out-of-range and unsupported values are rejected. Displayed values are rounded; calculations retain precision. Input-specific limits are reported alongside the field when exceeded.
Marathon distance · World Athletics ↗