Overview

Predict your marathon finish time from recent race or training results. This calculator uses the Riegel formula to project full marathon time from 5K, 10K, or half marathon performances, and provides pacing strategies for your target time.

Formula

Riegel Formula: T₂ = T₁ × (D₂ ÷ D₁)^1.06

T₁ = Reference time
D₁ = Reference distance
T₂ = Predicted finish time
D₂ = Target distance
Exponent 1.06 = Fatigue factor (accounts for pace decline over longer distances)

Example: 10K in 50 min → Marathon prediction
T₂ = 50 × (42.195 ÷ 10)^1.06 ≈ 234 min (3 h 54 min)

How to Use

1. 1Select a recent race or training distance (e.g., 10K).
2. 2Enter your finish time for that distance (e.g., 50 min).
3. 3Select the target distance you want to predict (e.g., marathon).
4. 4Your estimated finish time and target pace are calculated automatically.

Tips

• ✔10K or half marathon results predict marathon times more accurately than 5K times.
• ✔For a first marathon, add 10–15 minutes to the prediction for a conservative plan.
• ✔Temperatures above 15°C can add 5–15 seconds per kilometer on race day.
• ✔For hilly courses, add roughly 30 seconds per 100 m of elevation gain.
• ✔Weekly mileage below 50 km may reduce marathon prediction accuracy.

FAQ