I’ve written a number of articles about autosomal DNA triangulation.
I’ve created this repository to provide gather various resources all in one place to make it easier for you to find what you need.
Triangulation Concepts and Tools
What is triangulation, why it is important for genealogy, and how does one go about triangulating? More importantly, why do genealogists care?
In a nutshell, triangulation allows you to discover or confirm your ancestors or ancestral lines when:
- You match at least two other people (who are not close relatives) on the same reasonably sized segment of DNA.
- Those matches also match each other on a reasonably sized portion of the same DNA segment where you match both of them.
- You identify a common ancestor or ancestral couple who passed that segment to all of the people who match on that segment of DNA.
- Hit a Genetic Genealogy Home Run Using Your Double-Sided Two-Faced Chromosomes While Avoiding Imposters
This article explains chromosome matching and triangulation step-by-step to help you sort through your matches.
A chromosome browser is essential to genetic genealogy and specifically, to triangulation, allowing you to visualize your DNA matches on your chromosomes. This article starts at the beginning with what a chromosome browser looks like and explains each step along the way.
It’s important to understand that some people will match you, but won’t match either of your parents, or wouldn’t if your parents were both available to test. The technique of triangulation removes the issue of “false matches” which aren’t identical by descent, because you inherited that DNA segment from an ancestor through one of your parents, but are instead “identical by chance.”
If you’d like to utilize X matching, you’ll want to read this article. The X chromosome has a unique inheritance path, is treated differently by various vendors and you’ll need to evaluate X matches differently.
Genetic Affairs has numerous tools that facilitate and assist with different aspects of triangulation including their AutoClusters, AutoTree, AutoPedigree, AutoSegment and AutoKinship features in addition to their AutoSegment Cluster Tool at GEDmatch.
- Genetic Affairs – New AutoKinship Tool Predicts Relationships and Builds Genetic Trees
- AutoSegment Triangulation Cluster Tool at GEDmatch
How to Triangulate?
Each of the major vendors, except Ancestry, provides a chromosome browser along with some type of triangulation tool. Additionally, third parties who do not perform DNA testing offer great supplemental tools. GEDmatch and DNAPainter both provide triangulation tools, allowing you to take advantage of matches from multiple vendors.
I’ve written step-by-step articles detailing how to utilize triangulation at each vendor:
FamilyTreeDNA is the only vendor that provides built-in parental phasing, even if your own parents haven’t tested. You’ll want to either test at or transfer your DNA file (free) to Family Tree DNA, then pay the $19 unlock for advanced tools. As an added benefit, you can also test and obtain matches to your Y DNA (paternal or surname line) if you’re a male and mitochondrial DNA (mother’s matrilineal line) for either sex in order to further your genealogical research.
MyHeritage is the only vendor to incorporate a triangulation tool with shared matches and AutoClusters into their solution. Of course, MyHeritage also provides traditional genealogical research records that they combine with DNA matches and trees in their Theories of Family Relativity feature, showing potential tree connections between you and your matches to common ancestors. You’ll want to either test at or transfer your DNA file to MyHeritage (free), then pay the $29 unlock for advanced tools.
23andMe doesn’t call triangulation by that name, but they provide the functionality, nonetheless. While 23andMe doesn’t support trees in the normal genealogical manner, they are the only vendor who has created a sort of genetic tree, giving you an idea of how your closest matches may fit into a family tree positionally. You can’t transfer files to 23andMe, so if you want to be in their database, you’ll need to test there.
In the late fall or winter of 2020/2021, 23andMe made changes that broke triangulation the way it previously worked.
This article details the problem and provides step-by-step instructions for the workaround
GEDmatch does not provide DNA testing, but they do provide additional tools. You will find a number of people who have tested at Ancestry and other vendors, then transferred to GEDmatch to use their chromosome browser and other tools to obtain additional matches. GEDmatch is the only vendor who triangulates all of your matches at one time – providing a comprehensive report. You’ll want to transfer your DNA kit to GEDmatch (free) and subscribe to their Tier1 Level to utilize their advanced tools.
DNAPainter doesn’t provide DNA testing but does provide a critical service by facilitating the painting of your DNA matches on your chromosomes, identified by ancestor. This allows you to “walk the segment back in time,” meaning to identify the oldest ancestor to whom you can identify a specific segment. I utilize DNAPainter as a central location to house all of my identified segments from all vendors. You can get started by checking out the DNAPainter Instructions and Resources, here.
Testing and Transferring
It’s important to identify as many triangulated segments as possible, which means it‘s crucial to be in all the databases that support triangulation and provide tools.
All major vendors allow you to download your DNA raw data file once you’ve tested, but not all vendors support uploading other vendors’ files instead of purchasing their test.
You can upload (at least) recent versions of other vendors DNA data files to:
The following vendors do NOT support uploads, but you can download your DNA file from these vendors and upload to the vendors above:
I wrote step-by-step instructions about how to download your files from each vendor and uploading them to vendors who accept uploads in the article, DNA File Upload-Download and Transfer Instructions to and from DNA Testing Companies.
Up your genealogy game by transferring and triangulating.
I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.
Thank you so much.
DNA Purchases and Free Transfers
- FamilyTreeDNA – Y, mitochondrial and autosomal DNA testing
- MyHeritage DNA – ancestry autosomal DNA only, not health
- MyHeritage FREE DNA file upload – transfer your results from other vendors free
- AncestryDNA – autosomal DNA only
- 23andMe Ancestry – autosomal DNA only, no Health
- 23andMe Ancestry Plus Health
Genealogy Products and Services
- MyHeritage FREE Tree Builder – genealogy software for your computer
- MyHeritage Subscription with Free Trial
- Legacy Family Tree Webinars – genealogy and DNA classes, subscription-based, some free
- Legacy Family Tree Software – genealogy software for your computer
- Charting Companion – Charts and Reports to use with your genealogy software or FamilySearch
- Legacy Tree Genealogists – professional genealogy research
- Genealogical.com – lots of wonderful genealogy research books
I wish that I had a month’s vacation off to learn this material!!
In addition to the list I’d like to mention that our “Your DNA family” app is doing the triangulation automatically. That means you don’t have to group matches or select them, the app does all of this automatically (meaning identifying that matches are overlapping on the same chromosome and with enough technical overlap) and the user just needs to click a card (after the initial data download, the user usually has 250 and more what we call “Possible triangulation” groups. So 250+ chances to form a TG. You can see the app “in action” in this video: https://youtu.be/rdnb8y-y3XA
Roberta, Question for you regarding GEDmatch. When I find a DNA cousin and note the DNA on a specific chromosome at a adequate level, I have tried to do a segment search for that DNA hunk from other customers at GEDmatch. Everytime I do that, the original person who I found with that DNA does not come up in the segment search. I am not sure if I am doing something wrong or if I am just being wrong headed in these regards. thanks Bill
No, your thinking is correct. Have you done a 1 to 1 to see if that person does match you on that segment? They may have a bug that needs to be reported.
Roberta, yep they match me because that is where I found the DNA in the first place. I will report it. thanks Bill
My favorite triangulation tool didn’t make your list…. Louis Kessler’s Double Match Triangulator. Thank you for the great articles Roberta. Happy Holidays!!
Will FTDNA do phasing for a private tree on their site, or must it be public?
It’s just your tree that they use, so it can be either public or private.
Great article and resource. Thanks for providing this for everyone.
Thanks Roberta, your article has moved me along the path. I’ve bought Tier1 at Gedmatch and ran Triangulation, now what do I do with all the matches? Is there a next steps resource available. Thanks!
Start with your largest or closest match and begin identifying ancestors. I recommend painting each connection you find at DNAPainter.
Always enjoy your work and articles! But, there it is “but”, I’m trying to disprove a particular line that has shown up as the male ancestor five generations back in multiple trees.
I’ve done autosomal DNA, done the GedMatch (wow) and just wonder if autosomal triangulation is appropriate to use to disprove. Please, excuse my lack of technical terms and my apologies if you’ve answered this and I’m just not getting it.
Autosomal can’t be used to disprove a relationship that far back. All you can do it gather evidence of absence. Y DNA might be able to do the job though.
I always found Jim Bartlett’s “Segmentology” blog to be very helpful in understanding DNA segments and triangulation. He has spent years triangulating his matches to identify triangulated groups. He generously shares his experience and expertise on this site.
Yes, his blog snd articles are wonderful.
I thank you for all the work you do for us. I have 11 people who match me perfectly on Chromosome 15, identical start and identical end all with 29.2 cM. When I triangulate I get three of them neatly bundled in Cr 15, but when I add a fourth or up to seven different colors, the colors are identical in length, but there is a whitish subsection that is about a fourth the size of the total. Wish I could send you a photo of it. Any clues? Again, thanks.
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Do you think Ancestry will ever have a Triangulation feature? Do not understand
why they do not as it is a game changer.
No, I don’t think so. They have been very resistant.
On Ancestry I have found 2 shared matches each with at least 25cMs and each on ONE segment. As there is only one segment can I assume that the segments would have to triangulate??
No, they can actually match each other on a different segment entirely. And they can match you on different segments too.
Thanks Roberta. One more question. I have several matches that are 20-25 cMs in length that cover one segment. As a rule, would these one segment matches be consider a closer match than matches that are around 40 cMs but cover 3 to 4 segments?
No, I don’t think so. I don’t think there have been any studies but it world be interesting to look at a group of known 4th cousins or something like that and see.