VDOT is Jack Daniels’ single-number running-fitness score, built on the Daniels–Gilbert VO2max model. Enter any race result from 1500 m to the marathon and the calculator returns the VDOT that performance represents. Because equal VDOTs across distances reflect equivalent fitness, coaches and self-coached runners use the number to set training paces and to compare, say, a 5 km against a half marathon.
How it works
The calculator converts your race into a velocity, models the oxygen cost of that velocity, then adjusts for how long you can sustain it.
- Velocity:
v = distance (m) / time (min)in metres per minute. - Oxygen cost:
VO2 = -4.60 + 0.182258·v + 0.000104·v². - Sustainable fraction:
%VO2max = 0.8 + 0.1894393·e^(-0.012778·t) + 0.2989558·e^(-0.1932605·t), wheretis race time in minutes — shorter races allow a higher fraction. - VDOT =
VO2 / %VO2max, rounded to one decimal place.
Example
A 5 km in 22:30 gives v = 5000 / 22.5 = 222.2 m/min. Then VO2 = -4.60 + 0.182258·222.2 + 0.000104·222.2² ≈ 41.0, and %VO2max ≈ 0.946, so VDOT ≈ 41.0 / 0.946 ≈ 43.4.
| Race | Time | Approx. VDOT |
|---|---|---|
| 5 km | 25:00 | ~39 |
| 5 km | 22:30 | ~43 |
| 5 km | 20:00 | ~49 |
| 10 km | 40:00 | ~50 |
The whole calculation happens locally in your browser — nothing is uploaded.
Using VDOT to set training paces
A VDOT score is most useful not as a number to chase but as the key to a set of five training pace zones. Jack Daniels defined these as:
- Easy (E) — comfortable aerobic base building, about 60–79% of VDOT effort, conversational pace. Most of your weekly mileage sits here.
- Marathon (M) — your predicted marathon race pace, used for long tempo portions during marathon builds.
- Threshold (T) — comfortably hard, sustainable for about 20–60 minutes. The physiological target is the lactate threshold, and T-pace is roughly the pace you could hold for an hour race.
- Interval (I) — run at approximately your 5 km race pace. Designed to stress VO2max, intervals are typically 3–5 minute repetitions at this pace.
- Repetition (R) — faster than interval pace, run at roughly mile-race effort. Repetitions are short (30 seconds to 2 minutes) with full recovery; the target is speed and running economy.
Once you have your VDOT, look up the pace table in Jack Daniels’ Running Formula or a VDOT-based training app. Each pace zone follows mechanically from the score, so you do not need to guess whether a pace feels right — the math does the work.
Comparing performances across distances
Because equal VDOTs represent equivalent fitness, you can answer questions like “was my half marathon better or worse than my 5 km from last month?” by comparing VDOT scores. An improvement of two or three VDOT points over a training cycle is a meaningful fitness gain; a drop after a race on a hilly or hot course can signal conditions rather than fitness. Most coaches consider a VDOT change below one point to be within measurement noise.
Limitations
VDOT is inferred from a single race, so a bad day, an aided course, a tailwind, or racing in unusual heat or cold all contaminate the score. The model also assumes an honest all-out effort over the full distance. Paced runs, time trials stopped short, or results from very short distances (under 1500 m) are less reliable inputs. For best accuracy, use a certified flat road race result over 5 km or longer.