# Race Predictor Calculator

Created by Luis Hoyos
Last updated: Jul 04, 2022

Welcome to our race predictor calculator. This race time converter can predict or calculate the race time for a future run competition based on your previous running scores.

You can use this race time predictor as a:

• Marathon time predictor: if you input 26.2 miles or 42.2 km (official marathon length) as the new run distance.
• Half marathon time predictor: if you input 13.1 miles or 21.1 km (official half-marathon length) as the new run distance.

It's important to note that this race time predictor relies on certain assumptions we'll present in the next section.

## Assumptions made by this race predictor calculator

Before using this race predictor calculator, there are some points worth considering about the equation used (Riegel formula):

1. It assumes that the runner has done appropriate training for the distance he wants to run in the future. An excellent result on a 5 km distance doesn't mean the next day you're ready to run a half marathon as a person who's been training for months would do.
2. Assumes that the athlete doesn't have significantly above-average genetics for speed or endurance sports. That's because those people will always have better results than others.
3. The calculations for running times under 3.5 minutes and above 4 hours are less accurate.

## How this race predictor calculator works - Riegel's formula

This tool uses the Riegel's formula to calculate race time:

$T_2 = T_1(D_2/D_1)^{1.06}$

where:

• $T_1$ — Time achieved recently on distance $D_1$;
• $D_1$ — Distance achieved during $T_1$ time;
• $T_2$ — Predicted time for distance $D_2$; and
• $D_2$ — Distance for which $T_2$ time is foreseen.

Note that the equation presents a slight exponential that causes the relationship to not be 100% linear.

## Example: Using the formula to calculate race equivalency

Suppose you've run a half-marathon in two hours, and your next goal is to run a full marathon. If you want to predict the time the full marathon will take to you, you can use Riegel's formula to calculate that race equivalency. Follow these steps:

1. Identify the key terms.
• As a half-marathon length is 13.1 miles and took two hours, $D_1 = 13.1 \ \text{mi}$ and $T_1 = 3\ \text{hrs}$.
• As a full marathon length is 26.2 miles (twice a half-marathon), $D_2 = 26.2 \ \text{mi}$
2. Input the information in the Riegel's formula:
$T_2 = 3\ \text{hrs}(26.2 \ \text{mi}/13.1 \ \text{mi})^{1.06} = 6.255 \ \text{hrs}$
3. If 6.255 hour feels rare to you, use our time unit converter and you'll notice that $6.255 \ \text{hrs} = 6\text{h}\ 15\text{min}\ 17\text{s}$

That's it. You can also use this race time converter and verify the formula works well!

Luis Hoyos
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