Home / Cousin calculator
Cousin calculator
Pick what the shared ancestor is to you and to your relative — grandparent, great-grandparent and so on. The answer, the reason and the expected shared DNA update instantly.
They are your
second cousin once removed
Common ancestors: your great-grandparents. Expected shared DNA: 1.56%
Shorter branch = 3 steps → 3 − 1 = 2 → second cousin. Branches differ by 1 → once removed.
Cousin chart
Find your relationship to the shared ancestor along the top and your relative’s down the side. The square where they meet is how you are related. On a phone, scroll the chart sideways.
| Relative ↓ · You → | Child | Grandchild | Great grandchild | Great-great grandchild | 3rd great grandchild | 4th great grandchild | 5th great grandchild |
|---|---|---|---|---|---|---|---|
| Child | sibling | aunt/uncle | great-aunt/uncle | great-great-aunt/uncle | 3rd great-aunt/uncle | 4th great-aunt/uncle | 5th great-aunt/uncle |
| Grandchild | niece/nephew | first cousin | first cousin once removed | first cousin twice removed | first cousin three times removed | first cousin 4 times removed | first cousin 5 times removed |
| Great grandchild | great-niece/nephew | first cousin once removed | second cousin | second cousin once removed | second cousin twice removed | second cousin three times removed | second cousin 4 times removed |
| Great-great grandchild | great-great-niece/nephew | first cousin twice removed | second cousin once removed | third cousin | third cousin once removed | third cousin twice removed | third cousin three times removed |
| 3rd great grandchild | 3rd great-niece/nephew | first cousin three times removed | second cousin twice removed | third cousin once removed | fourth cousin | fourth cousin once removed | fourth cousin twice removed |
| 4th great grandchild | 4th great-niece/nephew | first cousin 4 times removed | second cousin three times removed | third cousin twice removed | fourth cousin once removed | fifth cousin | fifth cousin once removed |
| 5th great grandchild | 5th great-niece/nephew | first cousin 5 times removed | second cousin 4 times removed | third cousin three times removed | fourth cousin twice removed | fifth cousin once removed | sixth cousin |
The rule in two lines
- Cousin number = (the smaller number of generations down from the shared ancestor) − 1. Two steps each → first cousins; three steps each → second cousins.
- Times removed = the difference between the two counts. Two steps and three steps → first cousins once removed.
Half relationships (one shared ancestor instead of a couple) keep the same name with “half-” in front and share half as much DNA. For special cases, see half cousins and double first cousins.
Shared DNA by relationship
| Relationship | Average shared DNA |
|---|---|
| sibling | 50% |
| first cousin | 12.5% |
| first cousin once removed | 6.25% |
| second cousin | 3.13% |
| first cousin twice removed | 3.13% |
| second cousin once removed | 1.56% |
| third cousin | 0.781% |
| fourth cousin | 0.195% |
Averages from the coefficient of relationship. Testing companies and the Shared cM Project report real-world ranges, which are wide for distant cousins.
Relationship guides
- What is a second cousin?
- First cousin once removed
- What does “once removed” mean?
- What is a first cousin?
- First cousin twice removed
- Third cousin · third cousin once removed · fourth cousin
- Step-cousins (no shared ancestor)
- All relationship guides
Want to see real names instead of generations? Build your tree in the family tree maker and use How related? to tap any two relatives.
Questions
How do I work out what cousin someone is?
Find the nearest ancestor you both descend from. Count the generations from that ancestor down to you and down to them. Subtract one from the smaller number to get the cousin degree (first, second, third). The difference between the two numbers is how many times removed.
What is the difference between a second cousin and a first cousin once removed?
A second cousin is in your generation and shares your great-grandparents. A first cousin once removed is one generation above or below you — your parent’s first cousin, or your first cousin’s child.
Are my cousin’s children my second cousins?
No. Your first cousin’s children are your first cousins once removed. They are second cousins to your children.
What is a 1st, 2nd, 3rd and 4th cousin?
First cousins share grandparents, second cousins share great-grandparents, third cousins share great-great-grandparents, and fourth cousins share third-great-grandparents. Each step adds one generation between you and the shared ancestors.
Are cousins blood related?
Full and half cousins are: they descend from at least one shared ancestor. Step-cousins and cousins by marriage share no ancestor and no DNA through that link.
How much DNA do cousins share?
On average first cousins share about 12.5%, second cousins about 3.1%, third cousins about 0.8%. Real results vary because DNA is passed on in random chunks.