Training Paces Calculator

The Daniels-Gilbert Formula

The calculator converts a race result into a VDOT score using the Daniels-Gilbert formula — an estimate of effective aerobic capacity back-calculated from actual performance. Unlike a laboratory VO₂max value, VDOT already encodes your running economy: two runners with identical lab scores can have different VDOTs if one is more mechanically efficient. Each of the five training zones is then derived as a fixed percentage of the velocity at VO₂max implied by that score, producing paces matched to the specific adaptation each zone targets.

The Five Training Zones Explained

Easy (E) — roughly 60% of vVO₂max — is where the majority of running should happen: it builds capillaries, mitochondria, plasma volume, and cardiac stroke volume with minimal recovery cost. Marathon (M) pace targets the aerobic endurance specific to the marathon distance. Threshold (T) — near 88% of vVO₂max, approximately your 10K race pace — raises your lactate threshold, the single best predictor of sustainable long-distance race pace. Interval (I) at ~98% of vVO₂max (roughly 5K race effort) develops peak aerobic capacity. Repetition (R) above 100% of vVO₂max improves speed and running economy through short, fast efforts.

Refining with a Second Race

A single race assumes your endurance and speed fitness scale together, which isn't always true — a runner with a strong half marathon but an easier-than-expected 5K (or the reverse) will get skewed zones from one result alone. Tick "Refine with a second race result" and enter a shorter race: the calculator computes a VDOT score from each result and splits them by role rather than averaging them — the longer race sets Easy, Marathon, and Threshold pace, while the shorter race sets Interval and Repetition pace, regardless of which field you entered which result in. If you only have one recent result, the calculator still works fine on that alone — the second race sharpens accuracy, it isn't required.

The 80/20 Rule

Research on elite endurance athletes consistently finds approximately 80% of weekly training volume at Easy pace and 20% at Threshold or above, with very little time in the middle zone between them. Running everything at medium effort — the common recreational mistake — is too slow to drive VO₂max gains and too fast to allow full recovery, so it produces less adaptation per kilometre than the polarised approach. Use Easy pace for long runs and recovery days; reserve Threshold and above for structured workout sessions. See the full zone-by-zone breakdown for volume guidance.