VDOT Explained: How Jack Daniels Turns One Race Into Every Training Pace
What VDOT is, how Jack Daniels' Running Formula turns one race into easy, marathon, threshold, interval and repetition paces, and where it misleads.
VDOT is a single number that takes one race result and hands you every training pace you need. Here is what it means, why it works, and where it falls down.
What VDOT is
VDOT comes from Jack Daniels, the exercise physiologist behind Daniels' Running Formula, and his earlier work with Jimmy Gilbert. The notation is shorthand for V̇O₂max, where the dot means "per minute". True VO₂max is your maximum rate of oxygen use and needs a lab to measure.
Daniels' insight: you do not need the lab. Race speed already reflects your aerobic engine and your running economy together. VDOT is a performance-based VO₂max, the effective number that explains your race time once economy is folded in. Two runners with the same lab VO₂max but different economy get different VDOT values, because they race at different speeds. It is anchored to something you can verify any weekend: a race.
One race in, five paces out
Enter a recent all-out result and the model returns a VDOT and five training paces:
- Easy (E): conversational aerobic running for base and recovery.
- Marathon (M): the pace you could hold for 42.2 km.
- Threshold (T): comfortably hard, around your lactate threshold, as tempo runs or cruise intervals.
- Interval (I): hard running near VO₂max in repeats of 3 to 5 minutes.
- Repetition (R): short, fast reps for speed and mechanics, with full recovery.
Each pace maps to a physiological purpose. The model decides how fast so you can focus on showing up.
VDOT
49.8
Daniels running fitness score
| Zone | Range | What it trains |
|---|---|---|
| E | Easy / Long 4:54–5:53 /km | Aerobic base, capillaries, fat metabolism; most weekly volume. RPE 3–4, conversational. |
| M | Marathon 4:26–4:51 /km | Marathon-specific endurance and economy. RPE 5–6, steady. |
| T | Threshold 4:16–4:28 /km | Lactate threshold; comfortably-hard tempo and cruise intervals. RPE 7, ~1h race effort. |
| I | Interval 3:51–4:01 /km | VO₂max; 3–5 min hard reps. RPE 9, hard. |
| R | Repetition 3:19–3:42 /km | Speed, economy and running power; short fast reps with full recovery. RPE 9–10, fast and controlled. |
E · Easy / Long. Aerobic base, capillaries, fat metabolism; most weekly volume. RPE 3–4, conversational.
M · Marathon. Marathon-specific endurance and economy. RPE 5–6, steady.
T · Threshold. Lactate threshold; comfortably-hard tempo and cruise intervals. RPE 7, ~1h race effort.
I · Interval. VO₂max; 3–5 min hard reps. RPE 9, hard.
R · Repetition. Speed, economy and running power; short fast reps with full recovery. RPE 9–10, fast and controlled.
- Your VDOT of 49.8 is a single number that captures current running fitness (a 'VO₂max' adjusted for running economy). Every training pace is derived from it.
- VDOT comes from one recent, hard race or time trial. Use a result you raced all-out, ideally 5 km or longer; a half-marathon or 10 km gives the most stable estimate.
- Switch the units toggle to read paces per mile. As you get fitter, re-race; your VDOT and all paces will update.
- These are Daniels’ discrete training paces (E, M, T, I, R), not continuous zones: you run at each one for a specific purpose. The gaps between the harder paces (T, I and R) are intentional, not a glitch.
A PDF of your personalized results, with a QR code to reopen them anytime.
Why VDOT works
It is self-calibrating. The input is a race, so the output already accounts for your economy, your event and the conditions. You are not estimating a percentage of an estimated maximum heart rate.
Every pace has a job. Threshold work clears lactate, interval work stresses VO₂max, repetition work sharpens mechanics.
It is portable across distances. Daniels' tables use the same race-equivalence idea Pete Riegel formalised: a strong 5K predicts a credible 10K or half. The race time predictor does the same.
Where VDOT can mislead you
1. It assumes a balanced, well-trained runner. A fast-twitch 800m runner gets a flattering VDOT from a 5K and then fails at the predicted marathon pace. A pure ultra runner sees the opposite. The further the goal race sits from the input race, the more the prediction drifts.
2. Garbage in, garbage out. A race on tired legs, in heat or on hills understates you. A downhill or perfectly paced PR flatters you. Use your most representative recent effort.
3. Paces are not zones, and they ignore the day. VDOT knows nothing about today's fatigue, altitude or headwind. A heart-rate or RPE check stops an easy run turning into a threshold run by accident. Many runners pair VDOT paces with heart-rate zones for this reason.
How to use it
Race something in the last few weeks, ideally close to your goal distance. Drop the result into the VDOT calculator and build your week around the five paces: most volume Easy, a weekly Threshold session, Interval or Repetition work as the race nears, Marathon pace if you are aiming long. Re-test every four to six weeks so the paces move with your fitness.