Shared Centimorgan Project | How Am I Related to My DNA Matches?

“How I am related to my DNA matches? It’s a huge question. Most people have DNA matches whose names they don’t recognize.

Strategies for Finding Your Relationship to Your DNA Matches: The Shared cM Project

1. Ask them who they are.

Before you even start using the Shared Centimorgan Project, you can reach out to your DNA matches and ask them what they know about their birth roots. Between the two of you, you may be able to figure it out, based on what you know about your family trees.

But it’s not always easy to know how to reach out to your DNA matches. So before we even get to the whole centimorgans thing, we want to offer you our free downloadable guide, “Contacting Your DNA Matches.”

2. Find the total amount of DNA you share with your match.

Now, it’s possible your matches won’t know how you’re related, either. So now it’s time to turn to the DNA. The biggest clue you get with every single DNA match is your amount of shared DNA.

Every company tells you how much total DNA you are sharing with your match. Some of them also estimate your possible genealogical relationships. Here’s what you’ll see at each testing site:

23andMe: At 23andMe, you can see the percentage of shared DNA from the main DNA Relatives home page. You can use that figure with the Shared cM Project or you can click on a match to see the total number of shared cM.

Clicking on the little gray icon with an “i” in it will bring up a chart much like what we’ll describe below at the Shared cM Project, which presents various genealogical relationships that may fit your genetic relationship.

Family Tree DNA: On the main match page for your Family Tree DNA Family Finder results, you will see a genetic relationship range reported in the third column on your match list, followed by the total amount of shared cMs (1,414 cM in the first row, below):

Living DNA: Known for ethnicity reports especially specific for the British Isles, Living DNA is still building its DNA matching experience. It does report total shared DNA in both cM and as a percentage; clicking on the little “i” icon brings up a table of relationship possibilities, similar to The Shared cM Project.

MyHeritage DNA: The MyHeritage website reports the total amount and percentage of shared DNA, along with other figures, under Match Quality next to each of your matches. (Click on the question mark icon to see a table of possible relationships to each match.)

3. Take shared DNA data to the Shared cM Project

Blaine Bettinger spearheaded this collaborative effort we now call the Shared cM Project. He collected the shared cM data for known relationships from genetic genealogists just like you. The resulting free chart gives you a good estimate of how much DNA should be shared for different relationships. Here’s a quick peek (but look for yourself, as these get updated over time):

How to Use the Shared cM Project

Keep reading for how to use the Shared cM Project! This short video also demonstrates it for you—and comments on WHEN you actually NEED it.

For each DNA match, look up the total amount of shared DNA in the chart to get an idea of what kinds of genealogical relationship best fit the numbers. For example, if I share 69 cM with my match, we might be third cousins. But we might also be second cousins once or twice removed.

Jonny Perl and Leah Larkin have taken the Shared cM Project even further. They created an interactive Shared cM relationship chart on the DNA Painter website. Input the shared cM value to see the possible relationships and statistical probabilities for the likelihood of each of these relationships. This tool has TWO versions. One reflecting some original probabilities, and the Beta version (accessed by clicking the small, green “Beta with updated probabilities” on the left) with the most up-to-date estimates.

Notice in the above case that it is about 38% likely that you have one of those four listed relationships. A half 2C would share one of your 8 great grandparents. A 2C1R is a second cousin once removed, and indicates that this person is on a different generation than you are; they are either older or younger than you.

It is important to realize that these numbers are just estimates and honestly, as long as the probability of your relationship isn’t zero, you are probably OK. These numbers are just for you to use as a guide to help you know when you should start looking for your common ancestor with your match.

Next steps: Discovering the right relationships for your DNA matches

Now, how do you determine which is the correct relationship? It’s time for a two-prong approach.

Contact your DNA matches. I know. We said this already in the first step above. But sometimes it takes a couple of tries to get a real conversation going. It can be intimidating. That’s why we offer a free downloadable guide to contacting your DNA matches. If you didn’t grab it above, get it now:

Do genealogy research! It’s time to use traditional records and research skills to better understand the genetic clues in your family history mysteries. Read our free articles on the kinds of records and techniques that help you build a better family tree for your DNA matches.

Learn to Do the DNA—faster and with confidence

When it comes to identifying your DNA matches, you want to get it right. And you don’t want to go in circles or get lost in your analysis of who’s related to whom and how. (Believe me, it happens!)

My book is the ultimate step-by-step, do-it-yourself guide to figuring out how you’re related to your DNA matches. It even has special sections for what to do about specific situations that come up, like cousin intermarriages, endogamy, half-relationships, unexpected connections, unresponsive DNA matches and more.