The "Coefficient Of Inbreeding", or COI, commonly labeled F and expressed as a percent, is a measure of the amount of consanguinity in an individual's ancestry, in other words, how closely related offsprings parents are.

This tool allows you to calculate the inbreeding coefficient of a pedigree. Insert ancestor names or registration numbers in the pedigree form below, then press the "Calculate" button to get the inbreeding coefficient and breakdown. Blank fields will be ignored. Correct spelling is critical, as this program uses the entries to identify duplicate ancestors.

Important: The data you enter will not be saved automatically. To prevent data loss, save a configuration file before calculating the COI or refreshing the page.

    *Save a configuration file first!


    Show Generations

    Clear data from the above pedigree.

    Save Configuration File:
    Save As:
    A configuration file will be generated with the file name you enter here. Press the Save Settings button to save the file to your device. Example: my-pedigree.txt
    Load Configuration File:

    Only a configuration file from this calculator will work. The pedigree will be automatically populated with ancestors from the configuration file. Select a configuration file from your device, then press the Load Settings button.

    Simple examples of inbreeding coefficients.

    These numbers are correct if the common ancestors themselves are not inbred. If they are, the inbreeding coefficient will be higher.

    Relationship between parents Parents' common ancestor(s) Inbreeding coefficient
    Collaterally related parents
    SiblingsBoth parents25.000%
    Half-siblingsOne parent12.500%
    Both parents = grandparents12.500%
    Parent = grandparent6.250%
    Both parents = G-grandparents6.250%
    1st cousinsPair of grandparents6.250%
    Parent = G-grandparent3.125%
    Half-1st cousinsGrandparent3.125%
    1st cousins once removedPair of grandparents = G-grandparents3.125%
    Half-1st cousins once removedGrandparent = G-grandparent1.563%
    1st cousins twice removedPair of grandparents = 2G-grandparents1.563%
    2nd cousinsPair of G-grandparents1.563%
    Half-1st cousins twice removedGrandparent = 2G-grandparent0.781%
    Half-2nd cousinsG-grandparent0.781%
    2nd cousins once removedPair of G-grandparents = 2G-grandparents0.781%
    Half-2nd cousins once removedG-grandparent = 2G-grandparent0.391%
    2nd cousins twice removedPair of G-grandparents = 3G-grandparents0.391%
    3rd cousinsPair of 2G-grandparents0.391%
    Half-2nd cousins twice removedG-grandparent = 3G-grandparent0.195%
    Half-3rd cousins2G-grandparent0.195%
    3rd cousins once removedPair of 2G-grandparents = 3G-grandparents0.195%
    Directly related parents
    Self-fertilization, clones, or identical twins*self50.000%
    Parent-offspringself = parent25.000%
    Grandparent-grandoffspringself = grandparent12.500%
    G-grandparent-G-grandoffspringself = G-grandparent6.250%

    *This is not possible in organisms such as mammals, in which the parents must be of opposite sexes.

    Sample Pedigrees

    Click a button to load a sample pedigree.