running, cycling & swim math
Race numbers, worked out in your browser.
Pace, power, heart rate, and fueling calculators for runners, cyclists, and swimmers — built on the formulas coaches actually use. Free, fast, and accurate.
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Running
Pace, prediction, VDOT, VO₂max, zones, hills, treadmill, and age grading.
Pace Calculator
Solve for pace, time, or distance — and split it out.
OpenPace Converter
Convert between min/km, min/mile, km/h, and mph instantly.
OpenRace Predictor
Predict your 5K, 10K, half, or marathon from a recent race.
OpenVDOT & Paces
Get your VDOT and Daniels easy/threshold/interval paces.
OpenVO₂max
Estimate VO₂max from a race, a 12-min test, or 1.5 miles.
OpenYasso 800s
Turn 800 m repeats into a marathon estimate, or back.
OpenHR Zones
Five training zones from max HR, HR reserve, or threshold.
OpenRun/Walk
Blend run and walk intervals into an average pace and finish time.
OpenTreadmill
Treadmill speed and incline → outdoor pace and calories.
OpenGrade-Adjusted Pace
Convert hill pace to flat-equivalent effort, and back.
OpenAge Grading
Score your race against the world standard for your age and sex.
OpenCycling
FTP, power zones, power-to-weight, speed, load, and critical power.
FTP & Zones
Estimate FTP from a test and get your 7 Coggan power zones.
OpenPower-to-Weight
Work out your W/kg from FTP and see where you rank.
OpenSpeed ⇄ Power
Convert watts to speed (or back) from a physics model.
OpenTSS & IF
Quantify a session from power, FTP, and duration.
OpenGear Calculator
Gear ratio, gear inches, roll-out, and speed at any cadence.
OpenCritical Power
Find CP/critical speed and your W′ from two efforts.
OpenSwimming
Pace, pool splits, and critical swim speed in metres or yards.
Analyze your data
Drop in a GPS file and read your run or ride — distance, elevation, and splits, all in your browser.
Fueling
Carbohydrate, hydration, and sweat-rate math for long efforts.
Everyday
Quick answers — calories, calorie needs, steps, and distance.