Cousin Relationship Calculator

Count the generations from each person to the closest ancestor the two share — a parent is 1, a grandparent 2, and so on — and enter both counts. Or click a row and a column in the table.

A ↓ / B →ParentGrandparentGreat- Grandparent2x Great- Grandparent3x Great- Grandparent4x Great- Grandparent5x Great- Grandparent
ParentSiblingsAunt / Uncle Niece / NephewGreat- Aunt / Uncle Niece / Nephew2x Great- Aunt / Uncle Niece / Nephew3x Great- Aunt / Uncle Niece / Nephew4x Great- Aunt / Uncle Niece / Nephew5x Great- Aunt / Uncle Niece / Nephew
GrandparentAunt / Uncle Niece / Nephew1st cousin1st cousin, 1x removed1st cousin, 2x removed1st cousin, 3x removed1st cousin, 4x removed1st cousin, 5x removed
Great- GrandparentGreat- Aunt / Uncle Niece / Nephew1st cousin, 1x removed2nd cousin2nd cousin, 1x removed2nd cousin, 2x removed2nd cousin, 3x removed2nd cousin, 4x removed
2x Great- Grandparent2x Great- Aunt / Uncle Niece / Nephew1st cousin, 2x removed2nd cousin, 1x removed3rd cousin3rd cousin, 1x removed3rd cousin, 2x removed3rd cousin, 3x removed
3x Great- Grandparent3x Great- Aunt / Uncle Niece / Nephew1st cousin, 3x removed2nd cousin, 2x removed3rd cousin, 1x removed4th cousin4th cousin, 1x removed4th cousin, 2x removed
4x Great- Grandparent4x Great- Aunt / Uncle Niece / Nephew1st cousin, 4x removed2nd cousin, 3x removed3rd cousin, 2x removed4th cousin, 1x removed5th cousin5th cousin, 1x removed
5x Great- Grandparent5x Great- Aunt / Uncle Niece / Nephew1st cousin, 5x removed2nd cousin, 4x removed3rd cousin, 3x removed4th cousin, 2x removed5th cousin, 1x removed6th cousin

Cousin Relationship Calculator

Shows how two people are related to each other when they share a common ancestor. It also works in reverse: from a relationship named in a record, it shows how their nearest shared ancestor is related to each person — for first cousins once removed, one person’s grandparent is the other’s great-grandparent.

Using the calculator

The boxes — To find how two people are related, enter the number of generations each person is from their closest common ancestor. The result names the relationship and what the common ancestor is to each person: parent, grandparent, and so on. The chart below highlights the same answer simultaneously.

The chart — Click the row heading that matches how the common ancestor is related to Person A, and the column heading that matches the relationship to Person B. The highlighted cell where they meet names how the two people are related to each other, and the boxes above fill in to match. This also works in reverse: clicking the cell for a relationship found in a record shows what the shared ancestor is to each person. The chart opens at seven generations each way and can be extended.

Counting generations

What generation should I enter?

The count is how many generations back the common ancestor is from each person: a parent is 1, a grandparent 2, a great-grandparent 3, and each additional “great” adds one more. The count stops at the nearest ancestor the two people share. Counting from a more distant one raises both numbers and makes the two look more distantly related than they are.

Does it matter which person is A and which is B?

No. The relationship is the same whichever way round the two counts are entered; only the order of the two people in the result changes.

How should half relationships be handled?

The chart treats the common ancestor as a couple, both of them biological ancestors of each person. Two people who descend from the same man but different women, or the same woman but different men, share only one of the couple and are half-relatives: half-siblings, or half first cousins. They are counted the same way; “half” shows that only one side of that ancestry is shared. Older records and most families leave “half” out, so a relationship traced to a single shared person may be a half relationship even where the record doesn’t say so.

Cousin numbers and removal

What is a second (or third) cousin?

Cousins are numbered by which ancestor they share. First cousins share a grandparent, and each generation further back adds one to the number: second cousins share a great-grandparent, and third cousins share a 2x great-grandparent.

What does it mean to be cousins once removed?

When two people are related through an ancestor by a different number of generations, that difference is called “removed,” and the cousin number comes from whichever person is fewer generations from that ancestor. A person’s first cousin once removed can be either their great-grandparent’s grandchild or their grandparent’s great-grandchild — one generation up or one generation down, both use the same phrase. Records that use the phrase without qualification leave that direction to be worked out from ages or other records.