Running Calculators

Pace, race prediction, training zones and mileage planning. 12 calculators. The broader fitness and multi-sport tools sit under Fitness and Sports.

Race time prediction uses Riegel’s formula, and its limits are worth knowing before trusting the output. It extrapolates from one distance to another with an exponent of about 1.06, and it holds up well from 5k to half marathon. Beyond that it flatters people, because the marathon is not just a longer half: it is limited by fuelling and by muscular durability rather than by aerobic capacity alone. A 1:30 half predicts around a 3:08 marathon, and runners who have not done the long-run volume to support it reliably do not run it.

Treadmill equivalent pace handles the gap between belt pace and road pace. No air resistance and an assisted belt make treadmill running easier at the same number, and 1% incline is the usual correction at moderate speeds. At faster paces the correction grows.

Training zones are given from heart rate reserve rather than plain maximum heart rate, since the reserve method accounts for resting rate and gives noticeably different zone boundaries for fitter runners.