VDOT
calculator

Enter a race you have run and get your VDOT — Jack Daniels' single number for running fitness — plus the five training paces that follow from it, in min/mi or min/km. With what the number quietly assumes.

How the math works

VDOT is a VO2max-equivalent: the oxygen-uptake number your race performance implies, whether or not it matches your lab VO2max. It comes from two equations in Daniels and Gilbert's Oxygen Power (1979). The first gives the oxygen cost of running at a velocity; the second gives the fraction of VO2max you can hold for a race of a given duration. Divide one by the other and you have VDOT.

Each training pace is the velocity whose oxygen cost is a set fraction of your VDOT, from Daniels' zone intensities: Easy is 59–74% of VO2max, Marathon 84%, Threshold 88%, Interval 100% (the velocity at VO2max, "vVO2max"), and Rep about 112%. To turn a fraction back into a pace, we solve the oxygen-cost equation for velocity and convert with the exact mile factor (1 mile = 1.609344 km, NIST SP 811). The Easy cell shows the 74% ceiling — the fast end of easy, a pace to run at or slower.

Worked example

A runner posts 25:00 for a 5K (3.107 mi; 5.000 km). Running the equations:

• Race velocity: 5,000 m ÷ 25 min = 200 m/min
• Oxygen cost: −4.60 + 0.182258 × 200 + 0.000104 × 200² = 36.01 mL/kg/min
• Fraction of VO2max for 25 min: 94.0%
• VDOT: 36.01 ÷ 0.940 = 38.3

Training paces from VDOT 38, imperial first with metric in parentheses: Easy ceiling 9:44/mi (6:03/km), Marathon 8:48/mi (5:28/km), Threshold 8:29/mi (5:16/km), Interval 7:39/mi (4:45/km), Rep 6:59/mi (4:20/km). Those line up with Daniels' published VDOT tables to within rounding — the calculator computes them from the equations rather than reading a chart.

When this calculator is wrong

The most common way VDOT training goes wrong is not the paces — it is the distribution. Polarised-training research (Seiler 2010 and subsequent) points to roughly 80% of endurance running in easy Zone 1–2 and about 20% hard, with very little in the moderate "grey zone" that sits between Easy and Threshold. A VDOT chart hands you five paces and says nothing about how much time to spend at each; runners tend to drift their easy days toward Marathon or Threshold pace, which feels productive and blunts both the easy adaptation and the hard one. The exception is time-crunched athletes with fewer than four sessions a week, for whom some grey-zone running is unavoidable and probably fine.

• VDOT assumes a maximal, evenly-run race. The formula reads your race velocity as your current flat-course best effort. A race you paced conservatively, ran in heat, or covered on a hilly or windy course feeds it the wrong velocity — VDOT comes out low, and every pace it prints is too easy.
• It drifts as fitness changes. VDOT is a snapshot of the day you raced. Feed it a result from a different block of fitness — months old, or before a training gap — and the paces describe a runner you no longer are. Re-race, or re-time-trial, before trusting the number again.
• Easy is a range and Rep is an extrapolation. Easy pace spans 59–74% of VO2max by design, so the single number here is the fast ceiling, not a target to hit exactly. Rep pace sits above VO2max, where the oxygen-cost curve no longer strictly applies; Daniels sets it from 800 m–mile race speed, so treat the Rep cell as a starting estimate and check it against a short time trial.

What to do with the result

Use Threshold and Interval paces to anchor your hard sessions — tempo runs and cruise intervals at Threshold, VO2max work at Interval — and treat Easy as a ceiling for everything else, most of your weekly volume included. Marathon pace matters if you are training for the distance; otherwise it is a reference. Recompute after any race or hard time trial, and if the paces feel wrong in both directions across two weeks of consistent running, the race you entered is probably stale — run a fresh one rather than nudging the paces by feel.

Common questions

What is a VDOT number?

VDOT is a running-fitness score Jack Daniels back-calculates from a race: the VO2max-equivalent your performance implies. A faster time at a given distance means a higher VDOT. It is useful because the same number maps to a full set of training paces, so two runners with the same VDOT train at the same paces regardless of the race they got it from.

How do I calculate my VDOT?

Enter a recent race distance and finish time. The calculator finds your race velocity, the oxygen cost of that velocity, and the fraction of VO2max a race of that duration represents, then divides to get VDOT — the Daniels and Gilbert (1979) method. A 25:00 5K works out to about VDOT 38.

What race should I use?

A hard, evenly-run race on a flat course, from the last few weeks. Distances from about 1500 m to the half marathon give the cleanest VDOT; very short or very long efforts sit at the edges of the formula. If you only have an all-out time trial, that works too, as long as you actually ran it to exhaustion.

Are the training paces exact?

Threshold, Interval and Marathon paces are tightly defined fractions of VO2max, so those are reliable. Easy is a range by design — the calculator shows the fast ceiling, and slower is fine. Rep pace is an extrapolation above VO2max; Daniels sets it from short-race speed, so check it against an 800 m or mile time rather than trusting it to the second.

How often should I update it?

After any race or hard time trial. VDOT is a snapshot of the fitness you raced with, so a result from months ago, or from before a training break, will misprice your paces. If nothing has changed and you have not raced, the number holds.

Is a higher VDOT better?

For a given runner over time, a rising VDOT means improving fitness, which is the useful read. Comparing VDOT between different runners is fair as a fitness index but says nothing about who will win a given race — tactics, pacing and event specialisation all move race results independent of VDOT.