Running Calculators

Pace Calculator

Edit any field and the others fill in around it. Covers min/mile, min/km, mph, kph, distance, and time. Race estimates appear once you have a pace.

Pace Estimator

Enter a race result and get your Aerobic Index, an effective aerobic capacity derived from your performance, plus training paces across five intensity zones.

The oxygen cost of running at velocity v (m/min):

VO₂ = -4.60 + 0.182258v + 0.000104v²

Sustainable fraction of VO₂max for duration t (minutes):

%VO₂max = 0.8 + 0.1894393·e^(-0.012778t) + 0.2989558·e^(-0.1932605t)

Aerobic Index = VO₂ / %VO₂max. Zone percentages (59–110%) come from established exercise physiology research.

Critical Speed

Two race results at different distances give you Critical Speed (CS) and D-prime. CS is roughly your lactate threshold pace. D-prime is your reserve above that threshold in metres. It depletes when you run faster than CS and recovers when you slow below it.

CS = (d₁ - d₂) / (t₁ - t₂) (m/s)

D′ = d₁ - CS × t₁ (metres)

Training zones are percentages of CS velocity. Time to exhaustion at any speed above CS: t_lim = D′ / (velocity - CS).

Source: Burnley, M. & Jones, A.M. (2018). Power-duration relationship. Experimental Physiology 103(3), 279–297.

Race Predictor

T₂ = T₁ × (D₂/D₁)^1.06

The exponent 1.06 captures the fact that longer races are harder than a straight pace scale suggests. Most accurate when predicting distances within two or three times the input distance.

Source: Riegel, P.S. (1981). Athletic Records and Human Endurance. American Scientist 69(3), 285–290.