Inbreeding Coefficient Calculator (Wright's F)

Inbreeding Coefficient Calculator (Wright's F) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Education
Input types: select, number, textarea
Output type: json
Sample coverage: 4
API ready: Yes

Overview

Calculate Wright's inbreeding coefficient F from one or more common-ancestor paths, then estimate recessive affected-offspring risk using the disease allele frequency q. The calculator is intended for genetics education and pedigree analysis, not clinical decision-making.

When to use

When checking Wright's F for a relationship represented by known common-ancestor paths.
When comparing a pedigree result with reference values such as 0.25 for full siblings, 0.125 for half siblings, or 0.0625 for first cousins.
When illustrating how inbreeding changes recessive affected-offspring risk relative to the random-mating baseline q².

How it works

1Choose single-path mode for one common ancestor or multiple-path mode to sum contributions from several paths.
2Enter the generations from the sire and dam to each common ancestor, along with the ancestor's own inbreeding coefficient F_A when applicable.
3Provide the recessive disease allele frequency q and select the number of decimal places.
4The result reports Wright's F, the path count, affected-offspring risk q² + F·q·(1−q), and the risk multiplier relative to q².

Use cases

Verify pedigree exercises in population genetics or animal breeding courses.
Compare coefficients for half-sibling, full-sibling, and first-cousin relationships.
Demonstrate how allele frequency and inbreeding coefficient affect recessive risk estimates.

Examples

1. Calculate F for full-sibling mating

Genetics student

Background

A coursework pedigree shows two individuals who share both parents as common ancestors.

Problem

Calculate the combined contribution of the two independent 1,1 paths and estimate recessive risk at q = 0.01.

How to use

Select multiple-path mode, enter two lines of "1, 1, 0", set the allele frequency to 0.01, and use six decimal places.

mode: multiple
paths:
1, 1, 0
1, 1, 0
alleleFrequency: 0.01
decimalPlaces: 6

Outcome

The calculator returns F = 0.25 and an affected-offspring risk of 0.002575, or 25.75 times the random-mating risk.

2. Check a half-sibling pedigree

Animal breeding student

Background

A pedigree contains a mating between half siblings who share one non-inbred parent.

Problem

Find Wright's F from the single shared-parent path.

How to use

Choose single-path mode, set n1 and n2 to 1, enter 0 for the ancestor's F_A, and set q to 0.01.

FAQ

What does Wright's F represent?

It is the probability that two alleles at a locus are identical by descent.

What is the difference between single and multiple mode?

Single mode calculates one common-ancestor path; multiple mode sums contributions from all entered paths.

How do I enter multiple paths?

Enter one path per line as n1, n2, F_A. The F_A value is optional and defaults to 0.

How is recessive affected-offspring risk calculated?

The calculator uses q² + F·q·(1−q), where q is the disease allele frequency.

Can this result replace genetic counseling?

No. It is an educational estimate and does not replace clinical testing or professional genetic counseling.

mode: single
n1: 1
n2: 1
ancestorInbreeding: 0
alleleFrequency: 0.01
decimalPlaces: 6

3. Model a first-cousin relationship

Population genetics instructor

Background

An instructor wants to demonstrate the standard first-cousin coefficient using two shared-grandparent paths.

Problem

Sum two 2,2 paths and compare the result with the reference value 0.0625.

How to use

Select multiple-path mode and enter two lines of "2, 2, 0". Then provide the allele frequency and preferred decimal precision.

mode: multiple
paths:
2, 2, 0
2, 2, 0
alleleFrequency: 0.01
decimalPlaces: 6

Outcome

The two path contributions sum to F = 0.0625, allowing the corresponding recessive risk to be compared with q².

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Calculate F for full-sibling mating

2. Check a half-sibling pedigree

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3. Model a first-cousin relationship