The quality of an Autosomal DNA match is measured by the total percentage of shared DNA as well as the longest segment in common (measured in centimorgans, or cM). Autosomal matches are first compared to specific ranges that are defined for close relatives:
| Relationship | Total Overlap | Longest Segment |
|---|---|---|
| Parent / Child | 3539-3748 | 280-290 |
| Sibling | 2643-2802 | 50-141 |
| Nephew / Niece / Uncle / Aunt | 1526-2082 | 95-163 |
| Half-sibling | 1320-2100 | |
| Double First Cousin | 1480-1520 | |
| Grandparent / Grandchild | 1087-2297 | |
| Great- Grandparent / Grandchild | 572-1231 | |
| Great- Uncle / Aunt / Niece / Nephew | 550-860 | 60-135 |
| Half- Nephew / Niece / Aunt / Uncle | 684-1122 | 54-112 |
| 1st Cousin | 548-1034 | 50-182 |
| Half 1st Cousin | 320-330 | 30-35 |
| 1st Cousin Once Removed | 220-638 | 34-106 |
| Half 1st Cousin Once Removed | 195-205 | 23-33 |
| 1st Cousin Twice Removed | 107-426 | 21-64 |
| 2nd Cousin | 101-378 | 31-61 |
| 2nd Cousin Once Removed | 19-197 | 19-81 |
| 2nd Cousin Twice Removed | 12-73 | |
| 3rd Cousin | 43-150 | |
| 3rd Cousin Once Removed | 11-99 | |
| 4th Cousin | 5-50 | 0-24 |
| 5th Cousin | 0-33 | 0-10 |
If none of the above criteria are met, the match is grouped into four tiers:
- Immediate Relative - Likely to be a parent, child, sibling or half-sibling
- Close Relative - Likely to be first or second cousin
- Distant Relative - Likely to be a 3rd, 4th or 5th cousin
- Speculative Relative - Likely to be a 6th cousin or further
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