Running VO2max estimator
This tool estimates your VO2max — expressed as a VDOT score — from a single race result using Jack Daniels’ running formula. VDOT condenses your aerobic capacity and running economy into one number you can use to set precise training paces. Enter a 5K, 10K, or any race and instantly get easy, marathon, threshold, interval, and repetition paces tailored to your current fitness.
How it works
Daniels and Gilbert’s equations drive the estimate. First, average velocity is computed in metres per minute. The oxygen demand of that pace is:
VO2 = −4.60 + 0.182258·v + 0.000104·v²The fraction of VO2max you can hold for a race of duration t minutes is:
pct = 0.8 + 0.1894393·e^(−0.012778·t) + 0.2989558·e^(−0.1932605·t)Your VDOT is then VO2 ÷ pct. To produce each training pace, the tool inverts the oxygen-cost equation at a target percentage of VDOT and converts the resulting velocity back into a pace per kilometre.
Example and training zones
A 22-minute 5K gives a velocity of about 227 m/min and a VDOT near 48. From there the tool derives the full training pace range:
| Zone | Purpose | How it feels |
|---|---|---|
| Easy (E) | Daily mileage, recovery | Conversational, low effort |
| Marathon (M) | Long runs at race pace | Comfortably hard |
| Threshold (T) | Tempo runs and cruise intervals | ”Comfortably uncomfortable” |
| Interval (I) | 3–5 minute hard reps | Near maximal, very hard |
| Repetition (R) | Short fast strides, 400m reps | Fast and controlled, full recovery between |
Jack Daniels intended the five zones to be used in combination across a training week, not all at once. A typical week might include mostly easy mileage, one threshold session, and one interval session — with repetitions used sparingly for speed and form work.
VDOT vs lab VO2max
VDOT is sometimes called a “pseudo VO2max” because it is derived from race performance rather than a laboratory treadmill test. The distinction matters:
A lab VO2max is a direct measurement of your maximum oxygen uptake in millilitres of oxygen per kilogram per minute. It is essentially a ceiling — the largest engine you have. Two athletes can share the same lab VO2max and still run very different times, because running economy (how much oxygen you consume at a given speed) varies between people.
VDOT folds both factors together: your aerobic ceiling and how efficiently you use it. This makes it more predictive of race performance than lab VO2max alone, which is why Daniels chose it as the basis for training paces. A higher VDOT means faster paces across all zones, regardless of whether the gain came from a bigger engine or a more efficient stride.
Practical guidance
Use a genuine all-out race for the input — an easy run or a deliberately paced workout will understate your fitness and produce paces that are too conservative. Re-test every four to six weeks of structured training, or after any significant race, to keep your VDOT and derived paces current with your actual fitness level.
If your VDOT from a 5K and from a half-marathon differ significantly, the 5K number reflects your top-end speed capacity and the half-marathon number reflects your aerobic endurance. A large gap indicates which component of fitness to prioritise in your next training block.
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