Home / Cousin calculator

Cousin calculator.
What are we to each other?

Second cousin? Once removed? Pick how you're each descended from a shared ancestor and we'll name the relationship, the DNA you'd likely share, and whether you could legally marry in the US.

Start with the most recent ancestor you both descend from, like a grandparent or great-grandparent.

YOUR RELATIONSHIP
You are 1st cousins once removed.
≈ 433 cM shared on average Not sure? Check with DNA

The cousin chart.

Find your line in the rows and theirs in the columns. Tap any square to load it into the calculator.

Cousin chart: find your generation below the shared ancestor in the rows and theirs in the columns.
You are the ancestor's… / They are…ChildGrandchildGreat-grandchild2nd great-grandchild3rd great-grandchild4th great-grandchild5th great-grandchild
ChildSiblingNiece / nephewGreat-niece / nephew2nd great-niece / nephew3rd great-niece / nephew4th great-niece / nephew5th great-niece / nephew
GrandchildAunt / uncle1st cousin1st cousin 1× removed1st cousin 2× removed1st cousin 3× removed1st cousin 4× removed1st cousin 5× removed
Great-grandchildGreat-aunt / uncle1st cousin 1× removed2nd cousin2nd cousin 1× removed2nd cousin 2× removed2nd cousin 3× removed2nd cousin 4× removed
2nd great-grandchild2nd great-aunt / uncle1st cousin 2× removed2nd cousin 1× removed3rd cousin3rd cousin 1× removed3rd cousin 2× removed3rd cousin 3× removed
3rd great-grandchild3rd great-aunt / uncle1st cousin 3× removed2nd cousin 2× removed3rd cousin 1× removed4th cousin4th cousin 1× removed4th cousin 2× removed
4th great-grandchild4th great-aunt / uncle1st cousin 4× removed2nd cousin 3× removed3rd cousin 2× removed4th cousin 1× removed5th cousin5th cousin 1× removed
5th great-grandchild5th great-aunt / uncle1st cousin 5× removed2nd cousin 4× removed3rd cousin 3× removed4th cousin 2× removed5th cousin 1× removed6th cousin
Legal to marry in all 50 statesDepends on the stateIllegal everywhere

How cousins work, in plain English

Every cousin relationship comes down to two questions: which ancestor do you share, and are you the same number of generations down from them?

The number (1st, 2nd, 3rd) tells you how far back the shared ancestor is. First cousins share grandparents. Second cousins share great-grandparents. Third cousins share great-great-grandparents. Each step back roughly quarters the DNA you share.

"Removed" tells you how many generations apart you are. Your first cousin's kid is your first cousin once removed. Their kid is your first cousin twice removed. It works both ways, so your mom's first cousin is also your first cousin once removed. More on what "removed" means.

What is a second cousin?

Your parent and their parent are first cousins, which means you share a set of great-grandparents. Most people have dozens of second cousins and have never met them. Second cousins share about 3% of their DNA, around 229 cM. The full guide to second cousins.

Second vs. first cousin once removed

People mix these up constantly. Your first cousin's child is your first cousin once removed, not your second cousin. Your child and your first cousin's child are second cousins to each other.

How much DNA do cousins share?

On average, from the Shared cM Project: first cousins share about 866 cM, first cousins once removed 433 cM, second cousins 229 cM, third cousins 73 cM and fourth cousins 35 cM. The ranges overlap a lot, which is why a DNA match list says "2nd–3rd cousin" instead of one answer.

Can you marry your cousin?

Second cousins and beyond: yes, in all 50 states. First cousins: legal in about 17 states and DC, allowed with conditions in 6, and banned in 27. See the state-by-state map.

Your family tree says "probably not related."

Family trees miss adoptions, donors, affairs and the great-uncle nobody talks about. DNA doesn't. One check, one answer, free while in beta.

Check if we're related

Cousin questions.

What is a second cousin?

Second cousins share great-grandparents. Your parent and your second cousin's parent are first cousins. Second cousins share about 229 cM of DNA on average (roughly 3%), and marrying a second cousin is legal in all 50 US states.

What does "once removed" mean?

"Removed" means you are from different generations. Your first cousin's child is your first cousin once removed, and so is your parent's first cousin. Twice removed means two generations apart.

What is a first cousin once removed?

Either your first cousin's child, or your parent's first cousin. You are one generation apart and share about 433 cM of DNA on average.

What is a third cousin?

Third cousins share 2nd great-grandparents (great-great-grandparents). They share about 73 cM on average, and around 10% of third cousins share no detectable DNA at all.

What is a second cousin once removed?

Your parent's second cousin, or your second cousin's child. You share about 122 cM on average.

Is my cousin's cousin related to me?

Not necessarily. Your cousin on your mom's side has cousins on their dad's side who aren't related to you at all. You're only related if you share an ancestor.

What are double cousins?

Double first cousins happen when two siblings from one family marry two siblings from another. They share both sets of grandparents and about twice as much DNA as regular first cousins, close to half-siblings.