Relationship Degree Calculator
Determine the degree of relationship (consanguinity) between two individuals based on their family connection type.
Select a relationship type to begin.
Formulas Used
Civil Law Degree (direct line): Degree = number of generational steps between the two persons.
Civil Law Degree (collateral line): Degree = steps from Person A to common ancestor + steps from Person B to common ancestor.
Coefficient of Relationship (Wright, 1922):
r = Σ [ (1/2)L × (1 + FA) ]
Where L = total number of links (generational steps) through each common ancestor, and FA = inbreeding coefficient of the common ancestor (assumed 0 here).
For a single non-inbred common ancestor pair: r = 2 × (1/2)(steps_A + steps_B)
For direct-line relationships: r = (1/2)n where n = number of generations apart.
Assumptions & References
- Assumes no inbreeding in the family line (inbreeding coefficient F = 0).
- Full siblings share both parents; half-siblings share one parent.
- Civil law degree counts every generational step between the two individuals through the common ancestor.
- Canon law degree (used in some legal systems) counts only the steps to the common ancestor on the longer side.
- DNA percentages are expected averages; actual shared DNA varies due to recombination.
- nth cousins share great(n−1)-grandparents as their most recent common ancestors.
- References: Wright, S. (1922). Coefficients of Inbreeding and Relationship. The American Naturalist, 56(645), 330–338.
- Civil degree formula per most continental European legal codes (e.g., French Civil Code Art. 741–745).