Training Pace Calculator

VDOT is Jack Daniels' practical proxy for VO₂max, derived from actual race performance rather than lab testing. It combines your running economy and aerobic capacity into one number. A VDOT of 50 means you race like a runner with a VO₂max of about 50 ml/kg/min and average running economy; it is a performance score, not a lab measurement. Easy, Threshold, Interval and Repetition paces are derived from that value, and Marathon pace is the marathon time it predicts. As your fitness improves, your VDOT rises and all paces shift.

Every time you race or run a genuine time trial. For most runners building a base, that's every 6–12 weeks. Don't update based on a great training run, only use all-out race efforts. Using outdated paces (from a slower period) means your Easy runs are too easy and your Threshold isn't hard enough.

Daniels caps each kind of quality work as a share of weekly volume: Threshold up to about 10%, Interval up to about 8%, Repetition up to about 5%. The rest is Easy running, plus Marathon pace if you are training for one, which is why many coaches sum it up as roughly 80/20. Most recreational runners do the opposite: too much moderate effort, not enough true Easy, not enough truly hard. The result is chronic fatigue without adequate adaptation stimulus.

That's intentional. Easy runs build mitochondrial density, capillary development, and fat oxidation, all of which happen well at 59–74% VO₂max. Going faster doesn't accelerate these adaptations; it just adds stress you then have to recover from before the next quality session. The gap between your Easy pace and your race pace is the point.