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Pace Training Zones
Pace zones for running and swimming: Daniels VDOT training paces and Critical Swim Speed (CSS). One race result or time trial gives every training pace.
VDOT Calculator & Running Pace Zones
VDOT is Jack Daniels' single running-fitness number, combining VO₂max and running economy from one race result. A 5 km in 20:00 gives a VDOT of about 49.8. From that one number the model derives every training pace, Easy, Marathon, Threshold, Interval and Repetition, so all your zones come from a single race.
Critical Swim Speed (CSS) Calculator
Critical Swim Speed is your swimming threshold pace, found from two time trials: CSS = 200 ÷ (t400 − t200) in meters per second, and pace per 100 m = 100 ÷ CSS. A 400 m in 6:00 and 200 m in 2:50 give a CSS of about 1.05 m/s, or roughly 1:35 per 100 m, your sustainable threshold pace.
Running Race Time Predictor
A race time predictor estimates your finishing time at one distance from a result at another using Riegel's formula, T2 = T1 * (D2/D1)^1.06. Enter a recent race, such as 45:00 for 10K, and it predicts roughly 21:35 for 5K, 1:39:17 for a half, and 3:27:01 for a marathon.
Which pace model should you use?
Every pace model turns one honest performance into a full set of training paces. What differs is the performance it asks for, so choose the test you can do well rather than the one that sounds most precise.
| Model | Anchored to | Best for | You need |
|---|---|---|---|
| VDOT Calculator | VDOT, derived from a recent race result | Runners who want every training pace from a single race | A recent race you ran close to your limit |
| CSS Calculator | Critical Swim Speed, from a 400 m and a 200 m time trial | Swimmers setting a threshold pace per 100 | Timed 400 m and 200 m efforts on the same day |
| Race Predictor | Riegel's endurance exponent | Estimating a time at a distance you have not raced yet | One recent race result and a target distance |
Swipe sideways for every column. The fresher and harder the input race, the better every output pace.
A race result is the most honest test you own
No field test extracts as much from you as a race does. Pinning on a number, starting with other people and having something at stake produces an effort that a solo time trial rarely matches, which is why race-derived paces tend to be more accurate than test-derived ones.
The corollary is that a race you jogged is worthless as input. If you used an event as a training run, do not feed it into a pace calculator. Use the last race you genuinely emptied yourself in, even if it is a little older.
Pace lies on hills, in wind and in heat
Pace measures speed over the ground, not effort. Climbing a five percent gradient at the same physiological cost as a flat run can be ninety seconds per kilometre slower, and a headwind or 30 degrees of heat does something similar without any change in terrain.
So treat your pace zones as a flat, temperate, well-rested prescription, and switch guide on the days that are not. Uphill and in the heat, run to effort or power and let the pace be whatever it is. Chasing a flat-road number up a climb is how easy days turn into hard ones.
Frequently asked questions
How accurate is VDOT?
VDOT is accurate to within a few seconds per kilometre for most trained runners, provided the input race was genuinely maximal and reasonably recent. It is least reliable at the extremes: very new runners and athletes whose endurance is far ahead of their speed, or the reverse, will find one end of the range fits better than the other.
How recent does my race result need to be?
Within about six weeks for the paces to reflect your current fitness. Beyond three months you are training to an athlete who has since changed. If your only recent race was a poor day, use it and adjust upward slightly rather than reaching back to a result from a different season.
Why is my swim threshold so different from my running threshold?
Because threshold is specific to the muscles and the movement, not a single property of your body. Swimming loads the upper body and depends heavily on technique, so a strong runner can have a modest CSS. Set each sport from its own test and never transfer a threshold pace between them.
Should I train by pace or heart rate?
Use pace for the intervals and the flat, controlled sessions where it is a fair measure of work, and heart rate for long aerobic running where it settles and tells you the physiological cost. On hills, in wind and in heat, trust effort or power over pace, because pace stops describing what you are actually doing.
- VDOT Explained: How Jack Daniels Turns One Race Into Every Training PaceWhat VDOT is, how Jack Daniels' Running Formula turns one race into easy, marathon, threshold, interval and repetition paces, and where it misleads.
- How Eliud Kipchoge Trains (and Why He's Still Out There at 41)Kipchoge never runs a session flat out. The 80/50 week behind the greatest marathon career ever, and why it has him racing seven continents at 41.
- How Sifan Hassan Trains (One Engine, From 1500m to the Marathon)Sifan Hassan medals from 1500m to the marathon. The range behind it, and how one race result predicts your time at every other distance.