What is inbreeding?

Inbreeding is reproduction from the mating of pairs who are closely related genetically. It occurs when a dog has one or more common ancestors. A common ancestor is one that is present on both sides of the pedigree, so dogs with an inbreeding coefficient above zero need to be descended from at least one common ancestor. The degree of inbreeding is expressed with a formula first derived by the American geneticist Sewall Wright early in the 20th century where the symbol F represents the coefficient of inbreeding. This is the Wright's Coefficient of Inbreeding formula that we use in our calculation:

Typical coancestries between relatives are as follows:

Father/daughter, mother/son → 25% (1⁄4)
brother/sister → 25% (1⁄4)
Grandfather/granddaughter or grandmother/grandson → 12.5% (1⁄8)
Half-brother/half-sister, Double cousins → 12.5% (1⁄8)
Uncle/niece or aunt/nephew → 12.5% (1⁄8)
Great-grandfather/great-granddaughter or great-grandmother/great-grandson → 6.25% (1⁄16)
Half-uncle/niece or half-aunt/nephew → 6.25% (1⁄16)
First cousins → 6.25% (1⁄16)