Running Pace Calculator
Enter a recent race result to predict finish times at other distances and calculate your training paces. Powered by Riegel's race time prediction formula, tested across thousands of competitive runners.
Your Recent Race
Hours
Minutes
Seconds
Your Paces & Predictions
Enter your distance and finish time, then click Calculate.
📋 What Your Result Means
For educational purposes only — not medical advice.
Your race pace and predicted times are calculated using Riegel's endurance formula. Use the training zone table below to convert your race pace into structured daily workouts.
Training paces are derived from the Jack Daniels VDOT framework: Easy runs should feel conversational (65-75% effort), tempo runs feel comfortably hard (85-90%), and interval sessions are at or slightly above race effort (95-100%). The predicted times for other distances account for the natural slowdown as distance increases — the fatigue exponent of 1.06 represents the average aerobic endurance decay across competitive runners.
| Training Zone | % of Race Pace | Purpose |
|---|---|---|
| Easy / Recovery | 118-130% | Aerobic base, recovery |
| Tempo / Threshold | 107-112% | Lactate threshold development |
| Race Pace | 100% | Competition effort |
| Interval / VO₂max | 92-97% | Aerobic capacity development |
| Repetition / Speed | 85-90% | Economy, form, speed |
Important assumption: Riegel's formula assumes you have adequate training volume for the target distance. A 5K time will not accurately predict a marathon if you have never run more than 10 km. The predictions are most reliable when extrapolating up to about 4x your proven race distance. Beyond that, fueling strategy, pacing discipline, and long-run endurance become dominant factors that the formula does not capture.
Training distribution: Research supports spending roughly 80% of weekly volume at easy pace and 20% at high intensity. This "80/20" approach produces better race results than training at moderate intensity most days (Fitzgerald, 2014).
T₂ = T₁ × (D₂ / D₁)^1.06
Where T = time in seconds, D = distance in km, exponent 1.06 = fatigue factor
Race Pace: Pace = T (seconds) / D (km) → converted to min:sec / km
Training Paces: Based on Jack Daniels VDOT tables — derived from 5km race pace multiplied by zone-specific factors
Limitations
Riegel's formula assumes consistent fitness and training across distances. It works best when comparing similar distance types (road-to-road or trail-to-trail). Course difficulty, elevation, weather, and pacing strategy all affect actual race performance. The fatigue exponent of 1.06 is an average — ultra-endurance athletes often exhibit different curves.
✓ Strong EvidenceWant to learn more? Read our in-depth article: How to Calculate Running Pace and Predict Race Times →
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