Cousin Relationship Calculator
Family relationships past "cousin" get confusing fast — is it a second cousin, or a first cousin once removed? Enter how many generations back each of you is from your shared ancestor and this calculator names the exact relationship, whether that's siblings, an aunt/uncle, or an Nth cousin some number of times removed. Handy for genealogy research, building out a family tree, or figuring out how you're related to a relative you just met at a reunion.
Enter Generations to Your Shared Ancestor
Count generations as: 1 = a parent, 2 = a grandparent, 3 = a great-grandparent, and so on. It doesn't matter which person you enter first.
e.g. if the shared ancestor is Person A's grandparent, enter 2
e.g. if the shared ancestor is Person B's great-grandparent, enter 3
How Cousin Degrees and Removal Work
Every cousin relationship is built from two numbers: how many generations each person is from the ancestor they share. The smaller of the two numbers sets the cousin degree — first, second, third cousins, and so on — while the difference between the two numbers is how many times "removed" the relationship is, meaning the two people belong to different generations relative to the shared ancestor.
If both people are the same number of generations from the shared ancestor, they're plain cousins with no "removed" — for example, two people who are each two generations from a shared grandparent are first cousins. If one person is a generation further from the ancestor than the other, they're still related at the smaller person's cousin degree, but "once removed" — a generation apart. Two generations apart is "twice removed," and so on.
When the smaller distance is just 1 generation (a parent), the relationship isn't called a cousin at all — it's siblings if both are 1 generation away, or an aunt/uncle and niece/nephew relationship if one is further away.
Common Relationship Chart
Rows are cousin degree (based on the smaller generation count), columns are how many times removed.
| Degree | Same Generation (0 removed) | 1 Removed | 2 Removed |
|---|---|---|---|
| Sibling level | Siblings | Aunt/Uncle & Niece/Nephew | Grand-Aunt/Uncle & Grand-Niece/Nephew |
| 1st cousins | First Cousins | First Cousins, Once Removed | First Cousins, Twice Removed |
| 2nd cousins | Second Cousins | Second Cousins, Once Removed | Second Cousins, Twice Removed |
| 3rd cousins | Third Cousins | Third Cousins, Once Removed | Third Cousins, Twice Removed |
Frequently Asked Questions
What does "once removed" mean?
"Removed" describes a generation gap between two cousins. If your cousin's child is one generation further from your shared ancestor than you are, that child is your cousin "once removed." Two generations apart is "twice removed," and so on. The cousin degree itself (first, second, third) doesn't change — only the removal number does.
How do I know how many generations to the common ancestor?
Count upward from yourself: your parent is 1 generation, your grandparent is 2, your great-grandparent is 3, and so on. Do the same count for the other person up to the ancestor you both share, then enter both numbers above.
What's the difference between a cousin and a cousin once removed?
A plain "cousin" (no removal) means you and the other person are the same number of generations from your shared ancestor — you're peers, generationally speaking. "Once removed" means you're one generation apart — for example, your first cousin's child is your first cousin once removed, not your second cousin.
Are half-cousins calculated differently?
This calculator computes relationships based purely on generational distance from a shared ancestor, the same way regardless of whether the relationship is through a full or half sibling somewhere in the family tree. In casual use, half-relationships are often just described the same way as full ones (e.g. "half first cousins"), but the generation-counting math shown here stays the same either way.
Is any of my information saved or uploaded?
No. This calculator only works with the two numbers you enter and never uploads or saves anything — all the math happens right in your browser.
