VDOT

VDOT is a VO2max equivalent backed out of how fast you actually raced, not a lab measurement of your VO2 max. Daniels and Gilbert published it in "Oxygen Power" (1979), and Daniels carried it into "Running Formula". Two runners with different lab-measured VO2 max values but identical race times get identical VDOT scores, because VDOT folds in how efficiently you run and how long you can hold a given fraction of your capacity. That combination is closer to what decides a race than raw capacity is.

Daniels and Gilbert built VDOT from regression tables linking race distance and finish time to oxygen cost and the fraction of VO2max sustainable for that duration. In practice you look it up rather than compute it. Feed one recent, honest race result into the published tables or a calculator, read off your VDOT, then read off the recommended per-kilometer or per-mile paces for each training zone.

Recreational runners usually land somewhere in the low 30s to the 40s. Sub-elite competitive runners sit in the 50s and 60s. World-class distance runners go above 70 to 80. A VDOT is only as good as the race behind it: an all-out 5K reads cleanly, a casual training run does not, and the score goes stale as your fitness moves on.

The value of VDOT is prescriptive rather than descriptive. Once you have it, the same Daniels tables hand you Easy, Marathon, Threshold, Interval and Repetition paces calibrated to your fitness instead of to a generic percentage of max heart rate. That is the machinery behind most pace calculators on the internet, including the one on this site. Race time in, training paces out.

Running paces off a months-old VDOT, after your fitness has moved, is the usual error. Stale-VDOT zones come out systematically too easy if you have improved, or too hard if you have lost ground or come back from a break. VDOT also knows nothing about terrain, heat, altitude, or how tired you are today. It sets the target. It makes no promise that conditions will let you hit it.