About SwimRunPace

SwimRunPace is a set of endurance-sport calculators built around three questions: what pace do I need, what will that pace give me, and how should I train to hold it. The tools cover running, swimming and triathlon, because most of the people who use one of them use all three.

Where the numbers come from

Race-time prediction uses Pete Riegel's fatigue model, where time scales with distance to the power 1.06. Training paces use Jack Daniels' VDOT system, which converts a race result into a pseudo-VO2max and then inverts the oxygen-cost equation for each intensity. Calorie estimates use the ACSM metabolic equations for running and standard MET values for swimming. Critical swim speed is the slope between a 400 m and a 200 m time trial.

What we deliberately avoid

No tool asks for an account, an email address or a connected watch. No result is stored, and there is no training history to lose. Calculations run in JavaScript on your device, which is also why the site works offline once loaded.

Accuracy and honesty

Every formula is an approximation. Riegel assumes appropriate training for the target distance; VDOT assumes the race was maximal; the calorie equations assume average running economy. Where a number is an estimate rather than arithmetic, the page says so. If a result looks wrong, the formula section usually explains why.

Corrections

If a calculation is wrong, tell us via the contact page with the inputs and the expected result. Arithmetic errors get fixed quickly; disagreements about training philosophy are a longer conversation. See the privacy policy for data handling.

Frequently Asked Questions