# Race Predictor Calculator

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):

- 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. - 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. - 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:

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:

**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), $D_2 = 26.2 \ \text{mi}$

- Input the information in the Riegel's formula:

$T_2 = 3\ \text{hrs}(26.2 \ \text{mi}/13.1 \ \text{mi})^{1.06} = 6.255 \ \text{hrs}$ - 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!