Enter the weights and trait values into the calculator to determine the Selection Index. This calculator can also evaluate any of the variables given the others are known.

Selection Index Formula

The following formula is used to calculate the Selection Index.

SI = (W1 * T1) + (W2 * T2) + ... + (Wn * Tn)


  • SI is the Selection Index W1, W2, ..., Wn are the weights or importance given to each trait T1, T2, ..., Tn are the trait values

To calculate the Selection Index, multiply the weight of each trait by its corresponding trait value. Sum up all these products to get the Selection Index. This index is used in animal breeding and genetics to select individuals with the best combination of multiple traits for breeding.

What is a Selection Index?

A Selection Index is a statistical method used in animal and plant breeding to select individuals with desirable overall combination of traits for reproduction. It combines information from multiple traits and sources into a single numerical value for each individual. This value, or index, is then used to rank individuals and select the best ones for breeding. The goal is to maximize the genetic improvement across all traits of interest.

How to Calculate Selection Index?

The following steps outline how to calculate the Selection Index.

  1. First, determine the weights or importance given to each trait (W1, W2, ..., Wn).
  2. Next, determine the trait values (T1, T2, ..., Tn).
  3. Next, gather the formula from above = SI = (W1 * T1) + (W2 * T2) + ... + (Wn * Tn).
  4. Finally, calculate the Selection Index.
  5. 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.

Weights or importance given to each trait (W1, W2, ..., Wn) = 0.3, 0.5, 0.2

Trait values (T1, T2, ..., Tn) = 4, 7, 9