Cousins Calculator
Have you ever been at a family reunion and someone asks, “What kind of cousins are we?” only to find yourself completely stumped? Understanding cousin relationships—like second cousin once removed—can be surprisingly confusing. That’s where the Cousin Calculator comes in.
Our intuitive tool helps you determine the exact cousin relationship between two people based on their generational distance from a shared common ancestor. Whether you’re exploring a family tree or brushing up on genealogy terms, this tool makes it easy to identify how you’re related.
What Is the Cousin Calculator?
The Cousin Calculator is a free and simple online tool that helps determine your cousin relationship to another person. Whether you’re first cousins, second cousins, or third cousins once removed, this calculator figures it out instantly.
By entering how many generations each person is from your common ancestor, the tool determines your exact relationship—no need to memorize complex charts or do mental math.
How to Use the Cousin Calculator: Step-by-Step Guide
Using the calculator is simple and only takes a few seconds:
1. Determine Your Common Ancestor
This could be a grandparent, great-grandparent, or any shared ancestor.
2. Input Each Person’s Generational Distance
- In the “Person 1 Relationship to Common Ancestor” field, enter how many generations Person 1 is from the common ancestor.
- Do the same for Person 2.
✅ For example: If your great-grandparent is the common ancestor and you are their great-grandchild, that’s 3 generations.
3. Click “Calculate”
The tool will instantly determine your relationship and display it, such as:
- “2nd Cousins, 1x Removed”
- “3rd Cousins”
- “Siblings”
4. Use the “Reset” Button
Want to compare with another family member? Simply click Reset to clear the form.
Example: Who Is My 2nd Cousin Once Removed?
Let’s say:
- You are 3 generations removed from your common ancestor (great-grandchild).
- Your cousin is 4 generations removed (great-great-grandchild).
Input:
- Person 1: 3
- Person 2: 4
Result:
- 2nd Cousins, 1x Removed
That’s because the closest shared ancestor (your great-grandparent) is 3 generations from you and 4 from your cousin. The lower generation number minus one (3 – 1 = 2) gives the cousin level (2nd cousin), and the difference in generations (1) indicates “once removed.”
Why Understanding Cousin Relationships Matters
Understanding your relationship to family members isn’t just trivia—it has real-world value:
🧬 Genealogy Research
Accurate cousin relationships help you build detailed and correct family trees.
🧾 Legal Matters
Estate planning, inheritance laws, and citizenship questions can hinge on family relationships.
🤝 Reunions & Family Events
Avoid awkward conversations by knowing exactly how you’re related to Aunt Susan’s grandson.
🧠 Education & Learning
Great for students, teachers, and anyone studying anthropology or family lineage.
Extra Tips for Determining Relationships
- A “cousin” relationship always starts from the nearest common ancestor.
- The “removed” label refers to a generational difference.
- Two people who are the same number of generations from a shared ancestor are true cousins (e.g., both are great-grandchildren).
- If one person is one generation further down, they are once removed, and so on.
Frequently Asked Questions (FAQs)
1. What does “once removed” mean in cousin terms?
It refers to a difference in generations. If your cousin’s child is one generation below you, they’re your cousin once removed.
2. How do I know how many generations I am from a common ancestor?
Count how many steps up the family tree the ancestor is. For example, your parent is 1 generation, grandparent is 2, great-grandparent is 3, and so on.
3. Are siblings considered cousins?
No. If both people are 1 generation away from the common ancestor (their parent), the calculator will display “Siblings.”
4. What is a first cousin?
First cousins share the same grandparents. Each person is 2 generations away from the common ancestor.
5. How are second cousins different from first cousins?
Second cousins share the same great-grandparents (3 generations from each), while first cousins share grandparents.
6. Can cousins have different generation numbers?
Yes. If one cousin is a grandchild and the other is a great-grandchild, they are still cousins, but “once removed.”
7. Why does the calculator show “2nd Cousins, 1x Removed”?
That means one person is 3 generations from the shared ancestor, and the other is 4 generations. The cousin level is based on the shorter number minus 1.
8. What’s the highest cousin level the tool supports?
The tool works for any positive whole number input, though beyond 5th or 6th cousins, relationships become less legally and socially relevant.
9. Does this work for half-cousins?
The calculator assumes full biological relationships. Half-cousins would technically be one level closer in shared DNA, but still fall under the same cousin naming structure.
10. Is this tool useful for ancestry DNA results?
Yes, it helps you interpret genetic matches by clarifying what a given cousin term means.
11. Can I use this for step-family relationships?
No. This calculator only works for biological relationships based on shared ancestry.
12. Why is “3rd cousin twice removed” different from a 5th cousin?
They represent different relationships. Removed cousins are closer in actual family linkage than distant numbered cousins with no generational gap.
13. What happens if both people are 4 generations from the ancestor?
They’re 3rd cousins. That’s because 4 – 1 = 3, giving the cousin level.
14. How common are “removed” cousins?
Very common. Due to varying birth years in large families, many cousin relationships end up spanning multiple generations.
15. Can this tell me how much DNA I share with a cousin?
Not directly, but cousin level can help estimate. First cousins share ~12.5% DNA, while second cousins share ~3.125%, and so on.
16. Is it okay to marry a cousin?
Legally, this varies by country and region. First-cousin marriage is legal in some places and prohibited in others.
17. What’s a “double cousin”?
When two siblings from one family marry siblings from another family, their children are double cousins. This calculator does not account for that.
18. Can I use this for adopted family members?
Only if you know the biological relationships. Otherwise, use your personal understanding of family roles.
19. Does it work for distant ancestors like 7 or 8 generations?
Yes. Input any number greater than or equal to 1, and the tool will calculate appropriately.
20. What if I don’t know the exact generation?
Estimate based on known relationships—if you know someone is your great-great-grandchild, that’s likely 4 generations.
Conclusion
Understanding cousin relationships doesn’t have to be complicated. With the Cousin Calculator, you can instantly determine the exact familial connection between any two people who share a common ancestor. Whether you’re building a family tree, clarifying a genealogy report, or simply curious, this tool takes the mystery out of cousin terminology.
Try it now and bring clarity to your family connections—no genealogy chart required!