VDOT: definition, formula, example

VDOT is the number at the heart of Jack Daniels’ training system. The name comes from “V-dot-O2max”, the way physiologists write VO2max, but it is not measured in a lab. Daniels and the mathematician Jimmy Gilbert worked it back from race results in the 1970s: given how fast you ran a distance, what VO2max would explain it if your running economy were average? The answer is a single score that ranks your current running fitness, predicts what you could run at other distances, and gives you a set of training paces.

Because it comes from a performance, VDOT already includes things a lab VO2max leaves out: how economical your stride is and how large a share of your maximum you can hold for a whole race. Those three factors together explain most of endurance performance (Joyner and Coyle, 2008). That is why two runners with the same VO2max can have VDOTs several points apart, and why VDOT predicts race times better than VO2max does.

How VDOT is calculated

The Daniels-Gilbert formulas have two parts. The first gives the oxygen cost of running at a speed v, in metres per minute. The second gives the share of VO2max a runner can sustain for a race lasting t minutes: close to 100% for about 10 minutes, around 90% for 45 minutes, below 85% for a marathon.

The formulas hold from about 1,500 m to the marathon. Below that, races lean on anaerobic capacity; beyond it, fuelling and heat decide more than aerobic fitness.

A worked example

A runner finishes a flat 10K in 45:00.

• Speed: 10,000 m / 45 min = 222.2 m/min
• Oxygen cost: −4.6 + 0.182258 × 222.2 + 0.000104 × 222.2² = 41.0 ml/kg/min
• Sustainable share for 45 minutes: 0.8 + 0.1894 × e^(−0.575) + 0.2990 × e^(−8.70) = 0.907
• VDOT = 41.0 / 0.907 = 45.3

Run the formulas backwards and the same VDOT predicts about 21:42 for 5 km, 1:39:44 for the half marathon and 3:27:15 for the marathon.

Training paces come from fixed shares of VDOT, converted back into a speed with the oxygen cost formula. For a VDOT of 45.3:

• Easy (59 to 74%): 6:21 to 5:18 per km
• Marathon (the predicted marathon speed): 4:55 per km
• Threshold (88%): 4:37 per km
• Interval (97.5%): 4:15 per km
• Repetition (105%): 4:00 per km, or 96 seconds per 400 m

How to use VDOT in training

Each pace has a job. Threshold pace is for tempo runs of 20 minutes or cruise intervals such as 5 × 1 km with one-minute jogs. Interval pace is for repeats of three to five minutes, for instance 5 × 1,000 m with equal jogging recoveries, which is close to what French coaches call work at VMA. Repetition pace is for short, fast reps of 200 or 400 m with full recovery, aimed at economy. Easy pace covers most of the week.

Two habits keep the system honest. Set your VDOT from a recent race, not from the one you hope to run: training at goal pace before you have the fitness is the classic way to dig a hole. And raise it in small steps, one point after a good race or a block of sessions that felt controlled, rather than chasing every good day.

In OpenAthlete, the records page computes your VDOT from your strongest effort between 1,500 m and the marathon and shows the matching training paces. On this site, the pace charts use the same formulas, and the race predictor gives a second opinion with Riegel’s formula.

Limits

VDOT assumes your endurance matches your speed. A runner with a quick 10K and little mileage will usually miss the predicted marathon, often by several minutes, because the tables assume training suited to the distance. Hills, heat, wind and a poorly paced race all lower the score, so a VDOT from a bad day underestimates you. The sustainable share is an average curve: some runners hold a higher fraction of their maximum than others, and trail or ultra events are outside what the formulas were built for. Treat VDOT as a well-calibrated starting point, and adjust paces by feel and heart rate.