Pace Calculator

Method (Find Pace): total time is entered as hours, minutes, and seconds and converted to total seconds. Distance is converted to both kilometres and miles internally regardless of which unit was entered (1 mile = 1.60934 km), so both pace figures can be shown side by side. Pace per unit = total seconds divided by distance in that unit, then converted back into a minutes:seconds display (rounded to the nearest second). Speed per unit = distance in that unit divided by (total seconds divided by 3600), giving km/h and mph directly. Method (Find Time): a target pace (minutes and seconds per km or per mile, whichever unit is selected) is multiplied by the distance — after first converting the distance into the same unit as the pace, if they don't already match — to give total time in seconds, then formatted as HH:MM:SS. Worked example 1 (Find Pace): distance = 21.1 km, time = 1:45:00 (6,300 seconds). Pace per km = 6300 divided by 21.1, about 298.6 seconds, roughly 4:59/km. Distance in miles is about 13.11 mi, so pace per mile = 6300 divided by 13.11, about 480.6 seconds, roughly 8:01/mi. Speed = 21.1 divided by (6300/3600), about 12.06 km/h, about 7.49 mph. Worked example 2 (Find Time): distance = 5 km, target pace = 5:30/km (330 seconds/km). Time = 330 times 5 = 1,650 seconds = 27:30. If instead the target pace were entered as 5:30/mi with the same 5 km distance, the distance is first converted to miles (about 3.107 mi) before multiplying: 330 times 3.107, about 1,025 seconds, roughly 17:05 — a very different result, illustrating why matching the pace unit to the intended distance unit matters. Edge cases handled: - Zero or missing distance/time inputs: no result is shown rather than displaying a division-by-zero artefact like "Infinity" or "NaN." - Mismatched units between distance and pace in "Find Time" mode: handled automatically via the km/mile conversion factor, so entering a km distance with a per-mile target pace (or vice versa) still produces a correct result. - Very fast or very slow paces: the formatting logic handles any positive pace value, from elite marathon splits (under 3:00/km) to a slow recreational walk (over 15:00/km), without special-casing. Practical tip: when comparing your own training pace against a race result reported in the other unit system, always run it through a converter rather than approximating — the roughly 1.61x ratio between miles and kilometres means naive rounding (treating a mile as "1.5 km," for instance) can misjudge your pace by 5-10%, enough to meaningfully change a race-day strategy.