Tools

Calculators for runners and endurance athletes

All calculators run in your browser, no sign-up and nothing stored. Each page shows its formulas and sources.

Running

Pace calculator

Convert target time, pace and speed, with splits

Race time predictor

Predict 5k to marathon times from one result

VDOT and training pace calculator

Fitness score and training paces after Jack Daniels

Split calculator

Splits for even or negative-split racing

Pace converter

Convert min/km, km/h, min/mile and mph

Treadmill pace calculator

Turn speed and incline into pace and flat equivalent

km-effort calculator

Compare trail races with elevation gain

Heart rate zone calculator

Max heart rate and five training zones, incl. Karvonen

VO2 max calculator

Estimate VO2 max from Cooper test, race time or heart rate

Running calories calculator

Energy use and carbohydrate needs for runs and races

HYROX time calculator

8 runs, 8 stations and Roxzone to a finish time

Triathlon time calculator

Swim, bike, run and transitions from sprint to full distance

Swim pace and CSS calculator

Pace per 100 m and critical swim speed

FTP and power zone calculator

FTP from a 20-minute test, W/kg and seven power zones