Kinship Coefficient Calculator (Relationship r & Coancestry φ)

Kinship Coefficient Calculator (Relationship r & Coancestry φ) | 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

The Kinship Coefficient Calculator computes Wright’s coefficient of relationship r and kinship coefficient φ for two individuals using shared-ancestor paths. It can also estimate a child’s inbreeding coefficient F as the parental φ and classify the relationship by degree. Educational use only.

When to use

Estimate genetic relatedness from the generations separating two individuals from a common ancestor.
Sum contributions from multiple common-ancestor paths in a pedigree.
Calculate kinship φ and the expected child inbreeding coefficient F for an educational pedigree analysis.

How it works

1Choose Single common ancestor path or Multiple paths (sum over ancestors).
2For a single path, enter n1, n2, and the common ancestor’s inbreeding coefficient F_A.
3For multiple paths, enter one n1, n2, F_A line per path; F_A may be omitted and defaults to 0.
4The calculator applies r = Σ (1/2)^(n1+n2)(1+F_A), returns φ = r/2, estimates child F = φ, and provides a relationship-degree classification.

Use cases

Teaching Wright’s path method, kinship, and coancestry in genetics courses.
Checking textbook relationship values for full siblings, half siblings, and first cousins.
Exploring how multiple pedigree paths affect relatedness and offspring inbreeding.

Examples

1. Calculate relatedness between full siblings

Genetics student

Background

A student wants to verify the classic relationship value for two full siblings who share both parents.

Problem

A single shared ancestor path would omit the second parent and underestimate the relationship.

How to use

Select Multiple paths and enter two lines, one for each parent: 1, 1, 0.

mode: multiple; paths: 1, 1, 0\n1, 1, 0; decimalPlaces: 6

Outcome

The calculator returns r = 0.5, φ = 0.25, child F = 0.25, and classifies the pair as first-degree relatives.

2. Estimate first-cousin relatedness

Population genetics learner

Background

A learner is studying the two grandparent paths shared by first cousins.

Problem

The learner needs to combine both independent 2,2 paths to obtain the standard first-cousin value.

How to use

Select Multiple paths and enter two lines, one for each shared grandparent: 2, 2, 0.

FAQ

What does the coefficient of relationship r measure?

r estimates the proportion of genetic material two individuals share through common-ancestor paths.

What is the kinship coefficient φ?

Kinship φ is half the coefficient of relationship: φ = r/2.

When should I use multiple-path mode?

Use it when two individuals share more than one independent common-ancestor path, such as full siblings or first cousins.

What does F_A represent?

F_A is the inbreeding coefficient of the common ancestor used in a path calculation.

Is this calculator suitable for genetic counseling?

No. It is intended for educational use and does not replace professional genetic counseling.

mode: multiple; paths: 2, 2, 0\n2, 2, 0; decimalPlaces: 6

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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 relatedness between full siblings

2. Estimate first-cousin relatedness

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