Running calculators

All free, no sign-up required. Each calculator shows the underlying formula so you know exactly what you’re computing.

Pace Calculator

Convert between min/km, min/mile, and km/h. See finish times for 5K to marathon at any pace.

Finish Time Predictor

Predict your marathon or half-marathon from any known race result using the Riegel formula.

Heart Rate Zones

Calculate your 5 HR training zones using Karvonen or percentage of max heart rate.

VO2 Max / VDOT

Estimate VO2 max and VDOT from any race time. See equivalent training and race performances.

Boston Qualifier

Check your BQ time by age group and gender with cutoff buffer analysis for 2026/2027.

Splits Planner

Generate per-km or per-mile splits for even, negative, or positive split strategies.

Calorie Burn

MET-based calorie estimate by distance, pace, and body weight using ACSM compendium values.

How these calculators work

Every calculator on RunPaceLab implements its formula directly from the primary source — Daniels’ Running Formula, the Karvonen 1957 paper, Riegel’s 1981 race prediction equation, and others. The formulas are documented and unit-tested. Read the methodology.