What does cM shared mean in your DNA results? What does shared DNA mean? Learn the answers to these questions in this post, as well as where to find shared cM information on your DNA match list.
To begin the discussion, it is important that you understand two important definitions:
- cM: an abbreviation for the word “centimorgan”
- centimorgan: the genetic distance between two points on a chromosome
The word centimorgan is usually used to describe the length of a DNA segment. A genetic length, not physical length, however.
Understanding the meaning of shared cMs or shared DNA can help you learn more about how you are related to your DNA matches. Generally speaking, the more cMs someone shares with us, the closer our genealogical relationship.
Towards the end of this post, I will describe more about how to use centimorgans (cMs) to estimate your relationship with your DNA matches. The total amount of shared DNA, measured in centimorgans, is the most helpful information in estimating your relationship to someone.
In other words, once you understand what cM means in DNA, you will be well on your way to being able to use your genetic matches, also known as DNA relatives or DNA matches, to learn more about your living family members and your ancestors, as well as build your family tree.
What does shared cM mean?
Most of you probably arrived at this post because you saw “shared cM” on a DNA match profile, and you want to know what this stands for. You may even be curious about whether understanding this in more detail can help you guess how you and a match are connected.
The “relationship” that all DNA testing companies give us are just estimates, and we can use outside information, like our family tree, combined with shared cMs to make an even better estimate!
If you haven’t yet started building a family tree, today is a perfect time to get started. It’s free to get started building your tree on Ancestry, which is the site I use.
A subscription is not required, but I have one and recommend it.
As I mentioned above, cM in DNA stands for “centimorgan, and a centimorgan measures genetic distance, typically between two points on a chromosome. When two people have identical DNA between two points on a chromosome, we call this an identical DNA segment.
These two people with identical DNA might show up as DNA matches to each other, especially if the matching DNA segment is longer than about 6-7 cMs. Most DNA testing companies have a minimum threshold, or amount of DNA that two people must share, in order to count them as “matches” to each other.
The “size” of identical DNA segments is usually described using the word centimorgans. We can share a single DNA segment, or many segments, with our matches.
Generally speaking, sharing more, larger segments with a match implies a closer relationship. Fewer, smaller segments shared with a relative typically indicates a more distant genealogical relationship.
What does shared DNA mean?
Some people (and websites) describe the total amount of centimorgans shared between two people as “shared DNA”, which is very much is. When you see “shared DNA” on your DNA match list, understand that it means the same thing as shared centimorgans as defined above.
You might occasionally see “shared DNA” expressed as a percentage, especially on sites like 23andMe. You can use the calculator on DNA Painter to enter in the percentage shared and see the approximate centimorgan equivalent.
The calculator is also a helpful tool to see relationship possibilities based on a number of shared cMs or percentage of shared DNA. When you enter in number of shared cMs, you will see all of the relationship possibilities highlighted.
Where to find Shared cM on Ancestry DNA?
On Ancestry DNA, shared cM information will show up directly on your DNA match list. You can access your DNA match list directly from any page on the Ancestry site via the “DNA” tab on the top of the page, or from your DNA results dashboard page.
On your DNA match list, you will see the estimated relationship in bold and in normal text below it will say “Shared DNA”. The number that you see is the total number of centimorgans across the specified number of DNA segments.
What does shared cM stand for on Ancestry? As we noted above, shared cM means the total number of centimorgans shared. We can see the total amount DNA that we share with our matches on Ancestry directly on our match list, where it says “Shared DNA: XXXX cM across XX segments”.
To learn more about understanding your Ancestry DNA results matches, check out this post:
Where to find shared cM on 23andMe
If your DNA match’s privacy settings allow, you can access the total number of shared cMs, as well as other DNA segment data, using the 23andMe chromosome browser. Some customers have elected to not share certain information with their matches, so you may not be able to see exact chromosome data for all of your DNA matches on 23andMe.
The image below shows where to find the shared cM information on the 23andMe chromosome browser, which is called the “Advanced DNA Comparison Tool” and is accessible by hovering over the Friends and Family tab on the top navigation menu. Read “How to use the 23andMe Chromosome Browser” for more details.
For more about understanding your 23andMe results, you might find this post helpful:
Where to find Shared cM on Family Tree DNA?
Family Tree DNA displays shared cMs directly on the DNA match list. To see more detailed information about the location of the DNA segments, you must compare your DNA with that of your match in the FTDNA chromosome browser.
The image below shows where the shared cM information is located on your Family Tree DNA match list:
If you want to know more about your Family Tree DNA results, I wrote this post for you:
Where to find Shared cM on My Heritage
On your My Heritage DNA match list, you can see the shared cM information directly, as well as a lot of other information about your DNA match.
To the right of your DNA match’s name, you will see a column with some details about your connection with your match. Right next to where it says “Shared DNA”, you will see the total number of shared cMs as well as the percentage of DNA shared with your DNA.
The image below shows you exactly where you can see this information on your DNA match list (shown via the red arrow):
To learn more about your My Heritage DNA results, read this post:
You can use shared centimorgans to determine your relationship to a match
The shared centimorgan information that you find on your DNA match list can help you learn more about your connection to your DNA matches. I recommend this post to those who are learning more about using shared DNA to determine relationships:
Conclusion
I hope that this post has helped you understand more about shared cMs, total cMs, and how to find this information on your DNA testing site. If you have any questions about something that you read here, please join us in the discussion below.
Thanks for stopping by today!
Judy McMillion
Monday 13th of September 2021
How many cm would I have with my grandmother on my fathers side?
Judy McMillion
Monday 13th of September 2021
I haven’t any knowledge of who my grandmother on my father’s side is and thought that centermorgans could determine where I am related to her.
David Costelloe
Saturday 26th of June 2021
Great article. I've traced a paper family tree with paper records to a third cousin once removed who had taken a DNA test and is on Gedmatch.
Using "normal" setting on Gedmatch (7cM threshold for shared segments) => no matches. Using 4cM => 8.9cM Using 3cM => 22 cM
Her son, my third cousin twice removed has have the centimorgans of shared DNA, with some segments in common.
My interpretation is that this does not disprove a match, but does not provide strong evidence for it. Is that the case?
Jolanda
Tuesday 2nd of March 2021
I need help me and my first cousin has 947 cm across and 37 segments are we first cousins or half siblings..the percentage says 99% and 1% sibling and 1 % half cousin..so I really need to know how closely we are related because I am in search of my half sibling
Mercedes
Wednesday 3rd of March 2021
Hi Jolanda, Thank you so much for your question! We expect half siblings to share at least 1300-2300 centimorgans with us, so I would look more close at other relationship possibilities. Some of the possibilities at 947 cMs are first cousin, half-niece or nephew (i.e. the child of a half-sibling) or a half-aunt or uncle. If the match is a lot younger or a lot older than you (and depending on your age), they could even be a great-aunt or uncle. I hope this helps, and I wish you the best of luck finding your sibling! Sincerely, Mercedes
lnorm
Friday 26th of February 2021
If my DNA matches someone, or a family, will I get their names?
Mercedes
Friday 26th of February 2021
Hi! Yes, if you take a DNA test with any of the big companies (like Ancestry DNA, 23andMe, MyHeritage, Family Tree DNA), then you will be able to see the names of the people who match your DNA who have opted in to show up as DNA matches to other people who did their DNA tests with the same company. I hope that this helps you, Mercedes