A strong DNA match is generally considered to be 200 cM (centimorgans) or more.
Centimorgans (cM) represent the units used to measure genetic linkage. The higher the cM value shared between two individuals, the closer their relationship and the more DNA they have in common.
Here's a breakdown to provide context:
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What are Centimorgans (cM)? cM measure the likelihood that a specific DNA segment will be inherited together. Higher cM values suggest a stronger genetic relationship.
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Relationship Estimates:
- 3,400 cM: Parent/Child relationship (approximately 50% shared DNA)
- Approximately 2,300 - 3,900 cM: Sibling relationship (full sibling, approximately 50% shared DNA)
- Around 1,700 cM: Grandparent, Aunt/Uncle, Half Sibling (approximately 25% shared DNA)
- 850 cM: First Cousin (approximately 12.5% shared DNA)
- 425 cM: Second Cousin (approximately 3.125% shared DNA)
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Interpreting Matches: While 200 cM is considered a strong match, smaller cM matches aren't insignificant. They can point to more distant relatives. However, smaller matches may also include segments that are "identical by chance," meaning they look the same but aren't inherited from a common ancestor in a recent generation.
In summary, a DNA match of 200 cM or greater strongly suggests a close familial relationship.
