Half Marathon Race Pace Calculator (Predictor)

Race Time Prediction Formula:

\[ T_{new} = T_{ref} \times \left(\frac{D_{new}}{D_{ref}}\right)^k \]

Reference Distance:

Reference Time:

(hours:minutes:seconds)

Target Distance:

Predicted Race Time:

Predicted Pace (per km):

1. What is the Race Time Predictor?

The Race Time Predictor uses Riegel's formula to estimate your finish time for one race distance based on your performance at another distance. It's particularly useful for predicting half marathon times based on shorter race performances.

2. How Does the Calculator Work?

The calculator uses Riegel's formula:

\[ T_{new} = T_{ref} \times \left(\frac{D_{new}}{D_{ref}}\right)^k \]

Where:

\( T_{new} \) — Predicted time for new distance
\( T_{ref} \) — Your time at reference distance
\( D_{new} \) — New target distance
\( D_{ref} \) — Reference distance
\( k \) — Constant (typically 1.06 for endurance running)

Explanation: The formula accounts for the fact that running speed decreases non-linearly as distance increases.

3. Importance of Race Prediction

Details: Accurate race prediction helps runners set appropriate pace goals, plan training, and avoid starting too fast in longer races.

4. Using the Calculator

Tips: For best results, use a recent race time from a similar type of race (e.g., road vs. trail). The prediction becomes less accurate for very different distances (e.g., predicting marathon from 5K).

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this predictor?
A: It's reasonably accurate for most runners when predicting between common race distances (5K to marathon). Accuracy improves with more similar distances.

Q2: Why is the constant k=1.06 used?
A: 1.06 is an empirically derived value that works well for most runners. Elite runners might use slightly lower values (1.04-1.05), while beginners might use higher (1.07-1.08).

Q3: Can I use training run times?
A: Race times give more accurate predictions. Training runs often aren't run at maximum effort and may include stops.

Q4: What if my predicted time seems too fast/slow?
A: Consider your recent training volume, course difficulty, and conditions. The prediction assumes similar conditions and fitness level.

Q5: How should I use this for race pacing?
A: Use the predicted pace as a guide, but adjust for course elevation, weather, and how you feel during the race.