What is the Leeds Method?
The Leeds Method is a spreadsheet technique developed by genealogist Dana Leeds to sort DNA matches by colour according to grandparent line. It works best on matches sharing roughly 90 to 400 centimorgans - typically second to fourth cousins - because closer relatives often match on more than one line at once, and more distant matches give too little to go on.
How the method works
List your matches within the chosen cM range in a spreadsheet. Take the first match without a colour and assign it one. Then check which matches share DNA with that match (its "shared matches" list) and give all of those the same colour. Move to the next uncoloured match, pick a new colour and repeat the same step. After a few rounds this usually produces four colour groups, each roughly corresponding to one of your four grandparents. A match that overlaps with more than one colour group simply gets more than one colour - often a sign of a relationship through more than one line.
What it is useful for
The colour groups don't identify exactly who a match is, but they do show which grandparent line someone is likely related through. That makes it easier to place unknown matches, work towards an unknown parent or grandparent, or investigate a suspected non-paternity event (a mismatch between the biological and the known line of descent).
Limitations
The method becomes less clear-cut with inbreeding or endogamy (repeated intermarriage within the same family or community), since matches then more often land in several colour groups without that necessarily pointing to a separate relationship. The technique is platform-independent: it works anywhere a shared-matches list is available, including AncestryDNA, MyHeritage, 23andMe and FamilyTreeDNA.
Source
The Leeds Method was developed by genealogist Dana Leeds.
Read Dana Leeds's explanation →