How to Understand the Gedmatch Genesis One-to-Many Comparison

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Are you looking at your computer screen trying to figure out what the Gedmatch Genesis One-to-Many comparison results mean?  In this post, I will show you how to understand your Gedmatch Genesis results.  There is so much you can learn from them, and through them you have access to some really powerful information about your family history.

In this article, you will learn:

  • How to run the One-to-Many comparison tool on Gedmatch Genesis
  • What all of the different columns of your Gedmatch Genesis One-to-Many results stand for
  • Tricks for understanding how your matches on Gedmatch Genesis are related to you
  • Quick tips on how to get the most from your Gedmatch Genesis match list

(Haven’t decided to upload to Gedmatch Genesis yet?  Read “What is Gedmatch Genesis” or “How to Upload to Gedmatch Genesis“)

Let’s get started!  There is no need to feel overwhelmed by the long list of names and numbers.  I’ll help you decode everything so you will know what is important and how to interpret your results.

How to run the One-to-Many comparison tool on Gedmatch Genesis

While there are lots of tools on both Gedmatch and the newer, more refined site, Gedmatch Genesis, none of the tools compare to the One-to-Many.  It is recommended as a starting point for people using Gedmatch Genesis, and for good reason.  This is the way that you will locate new DNA matches that have not tested with your testing company.

There are two ways that you can access the tool:

  • From your dashboard (the screen that appears once you log in), you can just click on the kit number next to the name of the person whose kit you would like to analyze.  If you only have one kit on your account, then just click on your name.
  • The second way to run the tool is to click where it says “One-To-Many DNA Comparison Results” under DNA applications, about half-way down the screen on the right side.  Just enter in your kit # to see your results.

The site typically processes your request very quickly.  The results that appear are the top thousand or so people who have uploaded their DNA to Gedmatch Genesis whose DNA also matches yours.  They will be listed, generally speaking, in a descending order of shared DNA.

Please note that you will not be able to use this tool until your kit is completely done “batching” on the Gedmatch Genesis servers.  It usually takes a few hours for this process to complete.

What do the different columns mean in Gedmatch Genesis results?

The first few columns in your results are relatively obvious, but I will still go over them quickly to give you a few ideas of how to use the information that you find.

  • Kit:  The is the unique kit # assigned to your DNA match.  If you find a particular match that interests you, you should write down this kit number, or copy it into a document that you use to keep track of DNA matches.
  • Name:  This is the name, or the alias that your DNA match has chosen to display.  If there is an asterisk next to the name, then it is an alias.
  • E-mail:  The e-mail address displayed here is the one that your DNA match uses to log in to their Gedmatch and Gedmatch Genesis account.

When I am doing my research, my primary goal is to learn how my match and I might be related.  This usually involves trying to locate a family tree that the DNA match has created somewhere online.  Sometimes, my DNA matches have made trees on Ancestry, but other times, they might have started a website dedicated to their genealogy, or made a family tree on some other family tree sharing website.

Doing a quick search for the e-mail address, or “firstname lastname genealogy” in quotation marks can often lead to a family tree website that your match would actually like you to find.  If you do find something, you might be able to view their tree to see surnames in common, etc.  You might learn something new from the research they have already done.

But what do Largest Seg, Total cM, and Overlap mean?

These columns are often the ones that cause the most confusion, especially for users who are brand-new at this whole genetic genealogy experience.

What does largest seg, total cM, and overlap mean?

  • Largest Seg:  This is the length, measured in centimorgans, of the largest segment that you share with your DNA match.
  • Total cM:  This is the total of the length of all of the segments (over the size of the minimum threshold) that you share with your DNA match, measured in centimorgans.
  • Overlap: This is the total number of overlapping SNPs that you share with your match.  The concept of SNPs is an advanced one, but what you need to know is that any match with SNPs less than 150,000-200,000 are considered “low quality” and should probably be ignored in most cases.  The Gedmatch Genesis developers are working on refining their algorithms to improve match quality, so hopefully the low quality matches don’t even show up on our lists eventually.  For now, however, it’s good to know that you can potentially ignore some of your matches.

As an interesting observation, you can see on my mother’s Gedmatch Genesis results that she has two matches who tested with Living DNA – matches that she would not have seen had she not uploaded her DNA to Gedmatch Genesis.  They only share 161,000 overlapping SNPs with my mother, so I will be skeptical about their relationship as I look into their connection, but it is interesting.  We all hope that as the popularity of Gedmatch Genesis grows so that more and more people from different companies can compare their DNA.

How are my matches on Gedmatch Genesis related to me?

As a person who is just checking out your DNA matches on Gedmatch Genesis for the first time, you might be wondering how all of these people might be related to you.  There is no way to tell for sure 100% how someone is related to you just by shared DNA.  The only thing that I can tell you for sure is that if you share a lot of DNA, then you have a close relationship – you just have to figure out which close relationship applies.

The same is true for the matches that share less DNA with you.  If you share at least one segment 10 cM in length, and the SNPs are in a high range, then there is a decent probability that there is an actual common relative shared between you and your match.

When looking at your shared DNA:

  • the longer the segment, the more recent the common ancestor
  • the higher amount of total shared DNA, generally, the closer the relationship.  The only exception is if you share lots of really small segments with someone (like under 10 cM), which could imply that you are related to this person in many different ways

To determine your actual relationship, you will have to learn as much as you can about both of your family trees, and find where you connect.

How to get the most from my Gedmatch Genesis match list

As I mentioned before, it’s good to see if you can find a family tree somewhere online for your DNA match.  There are many other things that you can do to with your DNA match on Gedmatch Genesis to either find a connection or learn a little bit more about your shared ancestry.  Use some of the other tools available on Gedmatch Genesis:

  • Admixture (run an Admixture test on your DNA match’s kit # to see which ethnicity you share – this can help you narrow down which side of the family they might be on)
  • One-to-One (run a One-to-One test to see the exact location of your segments on your chromosomes that match – you can compare this with information you’ve learned about other matches to determine a connection)
  • People who match one or both of two kits (use this tool to find people who match both of you – sometimes, this can lead to more matches that have more complete family trees)
  • Contact them (using the e-mail provided, send them a note, along with your kit # and the kit # that you match with.  I recommend only contacting people that you share more than 25 cM with, and that you have at least a vague idea on which side of your family they are on)  Read about contacting DNA matches


I hope that this article helped you learn enough about your results to encourage you to explore them a little more.  If you have any questions, please feel free to post them in the comments.

Thanks for stopping by!


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How to Understand the Gedmatch Genesis One-to-Many Comparison
Are you looking at your computer screen trying to figure out what the Gedmatch Genesis One-to-Many comparison results mean? In this post, I will show you how to understand your Gedmatch Genesis results.
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