How much DNA do relatives actually share? A reference chart of average shared DNA by relationship, plus a full cousin chart for working out exact cousin terminology.
Sorted from closest to most distant. These are population-genetics averages, not measured results - see the FAQ below for why a real DNA test can vary.
| Relationship | Avg. shared DNA | Notes |
|---|---|---|
| Identical (monozygotic) twins | 100% | Formed from a single fertilized egg that split in two, so their DNA is essentially the same at birth. |
| Parent and child | 50% | A child inherits exactly half of each parent's autosomal DNA, so this figure doesn't vary the way sibling or cousin percentages do. |
| Full siblings | 50% | Each sibling gets a random half of each parent's DNA, so unlike the parent-child figure, the actual shared amount varies somewhat around this 50% average. |
| Grandparent and grandchild | 25% | One extra generation of recombination halves the parent-child figure. |
| Aunt/uncle and niece/nephew | 25% | Your parent's sibling shares roughly the same fraction of DNA with you as a grandparent does. |
| Half-siblings | 25% | Sharing only one parent instead of two roughly halves the full-sibling average. |
| Great-grandparent and great-grandchild | 12.5% | Each additional generation of separation halves the expected shared DNA again. |
| Great-aunt/uncle and great-niece/nephew | 12.5% | Your grandparent's sibling, one generation further removed than an aunt/uncle. |
| First cousins | 12.5% | Children of siblings - two generations of recombination separate you from your shared grandparent on each side. |
| Half-aunt/uncle and half-niece/nephew | 12.5% | Your parent's half-sibling. |
| First cousins, once removed | 6.25% | One generation separates you and your first cousin - for example, your first cousin's child, or your parent's first cousin. |
| Half first cousins | 6.25% | First cousins who share only one grandparent instead of two, because their parents are half-siblings. |
| Second cousins | 3.125% | You share a great-grandparent, not a grandparent - the most common match tier people ask "how much DNA" about after first cousins. |
| First cousins, twice removed | 3.125% | Two generations separate you and your first cousin, such as your first cousin's grandchild. |
| Second cousins, once removed | 1.5625% | One generation separates you and your second cousin. |
| Third cousins | 0.7813% | You share a great-great-grandparent. At this level it becomes common for a DNA test to detect no measurable shared DNA at all, even though the relationship is real. |
| Third cousins, once removed | 0.3906% | One generation separates you and your third cousin. |
| Fourth cousins | 0.1953% | You share a great-great-great-grandparent. Shared DNA at this level is frequently too small for a consumer DNA test to detect. |
| Double first cousins | 25% | When two siblings from one family marry two siblings from another family, their children share both sets of grandparents instead of one - doubling the usual first-cousin figure to roughly the same as half-siblings. |
Find your row and column by counting generations down from your most recent common ancestor (their child = 1, grandchild = 2, and so on) to see the exact relationship term.
| Generations down | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| 1 | Siblings | Aunt/Uncle - Niece/Nephew | Great-Aunt/Uncle - Niece/Nephew | Great-Great-Aunt/Uncle - Niece/Nephew | Great-Great-Great-Aunt/Uncle - Niece/Nephew | Great-Great-Great-Great-Aunt/Uncle - Niece/Nephew |
| 2 | Aunt/Uncle - Niece/Nephew | First cousins | First cousins, once removed | First cousins, twice removed | First cousins, three times removed | First cousins, four times removed |
| 3 | Great-Aunt/Uncle - Niece/Nephew | First cousins, once removed | Second cousins | Second cousins, once removed | Second cousins, twice removed | Second cousins, three times removed |
| 4 | Great-Great-Aunt/Uncle - Niece/Nephew | First cousins, twice removed | Second cousins, once removed | Third cousins | Third cousins, once removed | Third cousins, twice removed |
| 5 | Great-Great-Great-Aunt/Uncle - Niece/Nephew | First cousins, three times removed | Second cousins, twice removed | Third cousins, once removed | Fourth cousins | Fourth cousins, once removed |
| 6 | Great-Great-Great-Great-Aunt/Uncle - Niece/Nephew | First cousins, four times removed | Second cousins, three times removed | Third cousins, twice removed | Fourth cousins, once removed | Fifth cousins |
Map your actual relatives, however distant, with names, photos and stories. Free to start, no sign-up required.
Build your family treeFree forever · No email required to start
These figures are averages based on how DNA is inherited (the coefficient of relationship). Parent-child sharing is fixed at exactly 50%, but for every other relationship, random recombination during meiosis means the real amount two relatives share varies somewhat above or below the average shown here.
The degree (first, second, third cousin) is based on your closest shared ancestor - first cousins share a grandparent, second cousins share a great-grandparent. "Removed" counts a generation gap between cousins of the same degree, like your first cousin's child, who is your first cousin once removed.
Below about first cousins once removed, the amount of shared DNA gets small enough that random recombination can occasionally leave two real relatives with no detectable overlap on a standard DNA test, even though the paper-trail relationship is genuine.
No. Civil, canon, and religious law each count degrees of relationship using their own separate rules (often for marriage or inheritance purposes), which don't match the genetic percentages on this page.