Understanding CentiMorgans and Relationships

A comment which appears many times a day on DNA discussion groups is “DNA does not lie…”

  • DNA does not “lie”, but it does not often give a crystal clear answer either.
  • Even with a close DNA match, there will still be several possible ways in which the two of you might be related.
  • To work out which relationships might be relevant you need to consider:
    • the amount of cMs
    • relationships this could represent
    • and
    • which options would work for your search – consider shared matches, people’s ages, locations, known facts about the families.

Ancestry’s categorisation of matches often causes confusion…

Useful Resources for working out your relationship to a DNA Matches:

The Shared cM Project Tool v4

The DNA Detectives “Green Chart” by Christa Stalcup (Page 1)

The DNA Detectives “Green Chart” by Christa Stalcup (Page 2)

(reproduced with permission)

The documents below offer more details about interpreting DNA and relationships:


Click here to return to the Free Resources page