Daily AncestorCousin calculator
Second cousins share great-grandparents; "removed" means the two cousins sit in different generations, so a second cousin once removed is one step up or down from a second cousin.
A cousin relationship is fixed by two numbers: how many generations each person stands below the ancestor they share. Count those two steps and the name follows. This calculator does the counting for you and gives the name genealogists use, such as first cousins once removed or third cousins twice removed.
It is handy when a letter, an obituary, or a family Bible names someone as a cousin and you want to know exactly where that person fits, or when two branches of your tree meet and you need to describe how the living descendants are related.
How to use it
- Find the closest ancestor the two people share. For full cousins this is usually a couple, such as a set of grandparents.
- For the first person, count generations down from that ancestor: 1 for a child, 2 for a grandchild, 3 for a great-grandchild, and so on.
- Do the same count for the second person.
- Enter the two numbers. The answer names the relationship, and the cousin chart just under the calculator shows the same answer as a grid you can trace with a finger.
Worked examples
You: Grandchild. Your relative: Grandchild.
You are first cousins.
Two grandchildren of the same couple, through different children, share grandparents. That is the definition of first cousins.
You: Great-grandchild. Your relative: Great-grandchild.
You are second cousins.
Both are great-grandchildren of the same ancestor and stand in the same generation, so nothing is removed.
You: Great-grandchild. Your relative: 2x great-grandchild.
You are second cousins once removed.
The closer person sets the degree (3 generations down means second cousins). The one-generation gap between them is the "once removed."
You: Child. Your relative: Great-grandchild.
You are great-aunt or great-uncle and grandniece or grandnephew.
When one person is a child of the shared ancestor, the other is a niece or nephew line, not a cousin. Here you are the brother or sister of your relative's grandparent.
What is a second cousin?
Your first cousins are the children of your aunts and uncles: you share a set of grandparents. Your second cousins are the children of your parents' first cousins: you share a set of great-grandparents. Third cousins share great-great-grandparents, and the pattern keeps going one generation at a time.
A quick way to name the degree is to take the number of "greats" on the shared ancestor and add one. Shared great-grandparents (one great) make second cousins; shared great-great-grandparents (two greats) make third cousins.
What "removed" means
"Removed" counts the generations between two cousins. Your first cousin's child is your first cousin once removed, and so is your parent's first cousin. The relationship works in both directions: the same name describes each person from the other's side.
To find the degree when the two people are in different generations, always use the person who is closer to the shared ancestor. Then add one "removed" for each generation the other person sits below. This is why your second cousin's grandchild is still a second cousin, just twice removed.
Half cousins and double cousins
Half cousins descend from half siblings, so they share only one grandparent instead of a couple. Genealogists name them the same way and add "half": half first cousins, half second cousins. In this calculator, treat the one shared grandparent as the common ancestor and add "half" to the answer.
Double cousins are related through both of their parents. The classic case is two brothers who married two sisters: their children are double first cousins and share all four grandparents. You would run the calculator once for each side of the family.
Questions people ask
What is a second cousin once removed?
It is either the child of your second cousin or a second cousin of one of your parents. In both cases one of you shares great-grandparents with the other's parent, and there is one generation between you.
Is my cousin's child my second cousin?
No. Your first cousin's child is your first cousin once removed. Your children and your first cousin's children are second cousins to each other, because they share great-grandparents.
How do you read a cousin chart?
Put the shared ancestor in the top corner. Find the row for how many generations down the first person is and the column for the second person. The box where they meet holds the relationship.
What is the difference between a second cousin and a first cousin once removed?
Second cousins are in the same generation and share great-grandparents. A first cousin once removed is in a different generation: your parent's first cousin, or your first cousin's child.
Did old records use cousin the same way?
Not always. In older letters, wills, and diaries, cousin could mean any relative outside your direct line more distant than a brother or sister, such as a niece or nephew. Treat the word as a clue and confirm the link with other records.
How to cite this page
Daily Ancestor. "Cousin calculator." Tools. https://dailyancestor.com/tools/cousin-calculator. Last checked 2026-10-15.