What is in this collection
Thirty tools for the two questions every runner asks: what pace do I need, and what will that pace give me on race day. Start with the pace calculator if you have a distance and a time, or the race predictor if you have a recent result and a goal. The VDOT and Daniels tools turn one race into a full set of training paces, so easy days stay easy and hard days stay hard.
Running maths is unforgiving: a 5 s/km error is over three minutes in a marathon. Every tool here shows the unit it is working in, because min/mile and min/km are the most common source of pacing mistakes, and every split table uses even pacing unless it says otherwise.
How to choose a starting point
If you have a recent race result, start with the training pace tool for your sport: VDOT for running, critical swim speed for swimming. If you are planning a race, start with the pace or finish-time calculator for the distance, then check the goal against the predictor. Every page states its formula, so you can reproduce the number by hand.
Frequently Asked Questions
Which pace should I train at?
Most weekly volume should be easy — roughly 60–75% of the pace you could race a 5K at. Use the VDOT or easy pace tool to get a range, then stay at the slow end.
Why does the predictor disagree with my watch?
Watches estimate from heart rate and GPS; Riegel's formula estimates from an actual race result. A real race is the better input, especially for distances above 10K.
Do the tools work in miles and kilometres?
Yes. Pace inputs accept either unit, and the output shows both. Distance can be entered in miles or kilometres on the pages that take a custom distance.