Enter the fitness of the particular genetic variant and the fitness of the reference variant into the calculator to determine the selection coefficient. This calculator can also evaluate any of the variables given the others are known.

## Selection Coefficient Formula

The following formula is used to calculate the selection coefficient.

S = (W1 - W0) / W0

Variables:

- S is the selection coefficient
- W1 is the fitness of the particular genetic variant
- W0 is the fitness of the reference variant within a population

To calculate the selection coefficient, subtract the fitness of the reference variant from the fitness of the particular genetic variant. Then, divide the result by the fitness of the reference variant.

## What is a Selection Coefficient?

A selection coefficient is a measure used in evolutionary biology and population genetics to quantify the strength of natural selection. It represents the difference in fitness between a particular genetic variant and a reference variant within a population. A positive selection coefficient indicates that a variant increases fitness and is likely to become more common over time, while a negative coefficient suggests the variant decreases fitness and is likely to become less common.

## How to Calculate Selection Coefficient?

The following steps outline how to calculate the Selection Coefficient.

- First, determine the fitness of the particular genetic variant (W1).
- Next, determine the fitness of the reference variant within a population (W0).
- Next, gather the formula from above = S = (W1 – W0) / W0.
- Finally, calculate the Selection Coefficient.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

fitness of the particular genetic variant (W1) = 0.8

fitness of the reference variant within a population (W0) = 0.6