A centiMorgan (cM) is a unit of measure for DNA. It tells you how much DNA you share with another match. In general, the more DNA you share with a match the higher the cM number will be and the more closely related you are.
Using the shared centiMorgans tool can be very powerful in your own DNA match list. These instructions will show you how.
Every company tells you how much DNA you are sharing with your match.
Click on the company you tested with to see where to find your shared cM value
You can use this number to estimate or verify how closely related you are to that match. How? I thought you'd never ask! You can take that number into a table created by the collaborative efforts of the Shared Centimorgan Project.
Shared cM Project
Blaine Bettinger at thegeneticgenealogist.com spearheaded the effort that became the Shared cM Project. He collected the shared cM data for known relationships from genetic genealogists just like you. This free tool gives you a good estimate of how much DNA should be shared for different relationships.
How to Use the Shared cM project
To use the chart, take the total amount of shared DNA you have with a match, and look up that number in the chart to get an idea of what kind of genealogical relationship might best fit the genetics that you see. 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. Check out this video for help.
Now, how you determine which is the correct relationship? Simply put: do genealogy research! It’s time to use traditional records and research skills to better understand the genetic clues in your family history mysteries.
Jonny Perl has taken the Shared cM even farther. He has created an interactive Shared cM relationship chart. You can input the shared cM value and it will highlight the possible relationships for you. Click here to check it out!