Last updated: 2026-06-29

VDOT

VDOT is a performance index developed by exercise physiologist Jack Daniels to prescribe training paces from a single race result. It represents the effective aerobic capacity of a runner — combining true VO₂max with running economy — without requiring a laboratory treadmill test. Enter a recent race distance and finishing time, and the calculator returns a VDOT score and the five training pace zones derived from it.

How VDOT is calculated

The calculation rests on two relationships Daniels established from race data. First, the oxygen cost of running at velocity $v$ (in metres per minute) follows:

$\text{VO}_2 = -4.60 + 0.182258v + 0.000104v^2$

Second, competitive runners sustain a predictable fraction of their VO₂max over a given race duration $t$ (in minutes):

$\%\text{VO}_{2\text{max}} = 0.8 + 0.1894393\,e^{-0.012778t} + 0.2989558\,e^{-0.1932605t}$

VDOT is the VO₂ at race velocity divided by the fraction sustained:

$\text{VDOT} = \frac{\text{VO}_2}{\%\text{VO}_{2\text{max}}}$

A runner with VDOT 50 who held that score at every race distance would be equally fit by Daniels' definition — the score summarises overall aerobic performance regardless of which distance was used to derive it.

Training pace zones

Daniels defined five training intensities as fractions of the velocity at VDOT (called $v_\text{VDOT}$, the speed at which VO₂ equals VDOT). The inverse of that velocity, in seconds per metre, gives each zone's target pace:

Easy runs account for roughly 80% of weekly mileage in most Daniels plans. The T, I, and R zones are used selectively in quality workouts.

Worked example

A runner completes a 10 km race in 45:00.

From VDOT 45.3 the calculator derives $v_\text{VDOT} \approx 241$ m/min (approximately 4:09 per km). The five training paces follow directly:

These targets hold regardless of the distance run in any given workout — a 20 km Easy run and a 5 km Easy run use the same zone pace.

Equivalent race times

The equivalent-times table uses the Riegel power-law model with the standard exponent of 1.06 to translate the input race result across standard distances:

$t_2 = t_1 \times \left(\frac{d_2}{d_1}\right)^{1.06}$

The exponent greater than 1.0 reflects the reality that pace slows slightly as distance increases. The predictions are most accurate when the target distance is within a factor of two of the input distance. For distances far from the input race — predicting a marathon time from a 1500 m result, for example — the estimates carry more uncertainty.

Limitations and good practice

VDOT is calibrated on competitive race results produced at a genuine maximum effort on a flat, measured course. Time-trial performances run alone typically underestimate fitness by a few VDOT points. A result from more than 10–12 weeks ago may not reflect current fitness if training has changed significantly in the interim. Weather, altitude, and course profile affect race times but are not included in the model; adjust training paces by feel in extreme conditions.