How to organize your DNA matches

Guide · Updated July 2026

To organize your DNA matches, log each match with its total shared centimorgans (cM), use that total to predict the likely relationship, group matches that descend from the same ancestor, and record notes as you work each one out. The goal is to turn a list of names and numbers into a map of which matches belong to which branch of your tree.

The steps

1. Log each match. Record the match’s name or username, the testing company, and the total shared cM.
2. Predict the relationship. The shared cM total maps to a shortlist of relationships — 850 cM points to a half-sibling, grandparent, aunt or niece, for example. Use the shortlist plus known ages to narrow it.
3. Group by shared ancestor. Matches who also match each other usually descend from the same ancestral couple. Assign each match to the branch it belongs to.
4. Record how you are related. Once you identify the common ancestor, note it on the match, so the connection to your documented tree is captured, not just remembered.

Read the shared cM, do not guess

The single most useful number on a match is the total shared cM. It predicts the relationship far more reliably than a company’s label. Because the ranges overlap, treat the prediction as a shortlist and confirm it against your tree. For the full picture see shared centimorgans explained.

An honest boundary

AncestorOS logs DNA matches by manual entry — you record each match and its shared cM yourself, and it predicts the likely relationship from that total. It does not import a match file (CSV) from AncestryDNA, 23andMe, MyHeritage or FamilyTreeDNA, and it is not a DNA-testing service. If you have thousands of matches, focus on your closest and most informative ones first.