# Kinship Coefficient Calculator (Relationship r & Coancestry φ) Compute Wright's r = Σ (1/2)^(n1+n2)(1+F_A) and kinship φ = r/2 for two individuals, with reference values (full sib 0.5, half sib 0.25, first cousins 0.125) and relationship-degree classification. Child F = parental φ. Derived from Wright 1922, Falconer & Mackay, Hartl & Clark 2007, Jacquard 1970. Educational use only. > Canonical page: https://elysiatools.com/en/tools/kinship-coefficient - **Category:** Education - **Keywords:** kinship coefficient, coefficient of relationship, coancestry, coefficient of kinship, wright's r, inbreeding coefficient, pedigree analysis, consanguinity, identity by descent, first cousins relatedness, population genetics, genetics ## 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. ## Inputs - **Calculation Mode** (select): One common ancestor path, or a sum over multiple common ancestors. - **Generations from individual 1 to ancestor** (number): Generations from the first individual back to the common ancestor (single-path mode). - **Generations from individual 2 to ancestor** (number): Generations from the second individual back to the common ancestor (single-path mode). - **Ancestor's own inbreeding F_A** (number): The common ancestor's own inbreeding coefficient (single-path mode). - **Relationship paths (one per line)** (textarea): Multiple-path mode: one line per common-ancestor path as 'n1, n2, F_A' (F_A optional, default 0). Example for first cousins: two lines '2,2,0'. - **Decimal Places** (number) ## 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 - Choose Single common ancestor path or Multiple paths (sum over ancestors). - For a single path, enter n1, n2, and the common ancestor’s inbreeding coefficient F_A. - For multiple paths, enter one n1, n2, F_A line per path; F_A may be omitted and defaults to 0. - The 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. ## Frequently asked questions ### 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. ## Related tools - [Autosomal Dominant Pedigree Analyzer](https://elysiatools.com/en/tools/autosomal-dominant-pedigree): Compute AD offspring risk (Aa×aa 1:1, Aa×Aa 3:1, AA×any all affected), chi-square fit of observed children, and hallmark checks including male-to-male transmission that rules out X-linked dominant. Derived from Griffiths, Hartl & Clark 2007, StatPearls, OMIM. 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