How Much DNA Do You Share with Your AncestryDNA Matches?

AncestryDNA doesn't make it intuitive to find out how much DNA you share with your matches - but they do provide the information. This information is important because it helps determine if a match is one that deserves focus.

The main thing to remember is that you need to "View the Match" in question, and then click the small "i" icon below the "predicted relationship" line.

How to Locate a DNA Match

Unfortunately, AncestryDNA doesn't allow people to search for DNA matches by username. However, you can search for matches who show a specific surname in their tree:

Step 1 - Navigate to the correct set of matches

• Navigate to your Ancestry DNA page
• If you manage multiple DNA tests, click "View another test" at the top right of the page and select the appropriate test

Step 2 - View All DNA Matches

• Click "View all DNA matches" at the bottom of the center column; you'll be presented with a list of perhaps hundreds of pages of matches

Step 3 - Search matches for a specific ancestral surname

• Click "Search matches" at the top right of the page
• Enter the surname you want to search for at the top right; this searches public trees for people who descend from someone with that surname

 

This method doesn't work for people who don't have Ancestry trees - or whose trees are limited. Instead, view a match of someone who's a known member of the line of interest. Click the center button, "Shared Matches," and then select the appropriate person. This sometimes takes a couple of tries to find someone who matches both you and the person in question.

Inspect the Amount of Shared DNA

• Once you've located the appropriate individual, click "View Match" in the right column
• At the very top of the match, you'll see a predicted relationship; click on the "i" icon below it next to the "Confidence Level"
• You'll then see a pop-up box that says something like "121 centimorgans shared across 3 DNA segments
• Record those figures

 

Interpreting Shared DNA Amounts

Now that I know that "Max" and I share 121 centimorgans (cM) of DNA, I can use that information to narrow down our possible relationship. Because DNA inheritance is somewhat random, the amount of DNA shared by two related people will vary. References usually quote an average amount of shared DNA between, for example, first cousins as 880 cM - but the actual amount can vary between about 533 cM and 1379 cM. For close relationships, people share a great deal of DNA (parents and their children share about 3471 cM - as do identical twins) and the range is narrower: 3266 cM to 3720 cM.

DNAPainter provides a great tool to determine possible relationships. Go to their Shared CM Project Tool and enter the amount of shared DNA. As shown on the Shared CM Project table, the 121 cM I share with Max could mean we're as close as a first cousin once removed or as distant as a fourth cousin. In fact, "Max" is my third cousin once removed.

The table is most helpful for close relationships - and can be extremely useful for adoptees searching for immediate family members. More distant relationships aren't categorizable - and are sometimes complicated by relationships across multiple lines. It's important to remember that 10% of third cousins don't match - and 25% of fourth cousins don't match. These tools are helpful, but rarely exact.