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What is Unweighted Shared DNA on Ancestry?

Do you want to learn about the unweighted shared DNA data on Ancestry? In this post, find out the differences between weighted and unweighted shared DNA, how this information is calculated and how to use it in researching your connection to your DNA matches.

You will learn:

  • Where to find unweighted shared DNA on your DNA match list
  • Exactly what is unweighted shared DNA
  • What’s the difference between weighted and unweighted DNA
  • How to understand the weighted shared DNA details

The unweighted shared DNA feature is new on Ancestry. Prior to September, 2020, we could only see the total amount of shared DNA along with the total number of shared DNA segments.

What is Unweighted Shared DNA on Ancestry

Now, we have access to the total amount of shared DNA, the size of the longest segment, and the total amount of unweighted shared DNA. This is fantastic, but we often have more questions as we get access to more information.

I am really happy with the total amount of unweighted DNA now listed for our DNA matches. I hope that the information that you find in this article helps you understand this information and learn more from your match list.

Where to find unweighted shared DNA details on Ancestry

To find the unweighted shared DNA, you must first choose a DNA match to examine. Then, click on the blue link containing the total shared DNA and number of DNA segments that shows up after “Shared DNA”.

The image below indicates exactly where you should click to access the unweighted DNA information:

This image shows where to click on Ancestry DNA match to find the unweighted DNA information, as well as other shared DNA details.  It it a link right next to the words "Shared DNA" located on the DNA match profile

A window will appear that contains more details about the DNA that you share with your relative. You’ll see the total number of shared centimorgans, the number of DNA segments, the total number of unweighted shared DNA, and the size of the longest DNA segment:

In the image above, you can see that I share 76 cMs of total DNA with my match. The longest segment of DNA is 27 cMs, and the amount of unweighted DNA is 83 cMs.

To find more about what all of this information means, keep reading. I’ll discuss it more in detail below.

What is unweighted DNA on Ancestry?

Unweighted shared DNA on Ancestry is the total number centimorgans shared between two DNA matches before Ancestry’s Timber algorithm. “Weighting” by the Timber algorithm assigns more weight to shared DNA segments that are likely due to an ancestor that could be identified with family tree research.

Timber identifies DNA segments that are shared between large numbers of Ancestry DNA customers who share common geographic origins. While these segments do indicate a common ancestry, the most recent common ancestor is not not likely to be within the genealogical time frame.

What is the difference between weighted and unweighted DNA?

Unweighted shared DNA is the total amount of DNA shared between two Ancestry DNA customers before the application of the Timber algorithm that assigns less weight to DNA segments that were unlikely to have been inherited by a recent ancestor.

Timber filters out entire DNA segments and weights DNA segments more likely to be from recent common ancestors in order to provide us with a DNA match list that is more useful for genealogy research.

Sometimes, you will find that the unweighted DNA is more than the total shared DNA. How is this possible?

The answer is due to the Timber algorithm that I discussed above. When Timber assigns a lower value to a DNA segment that is shared between thousands or tens of thousands of Ancestry DNA customers, it reports it as a smaller segment than it actually is.

We will only notice this phenomenon when we have matches with whom we only share one segment of DNA. This is because we can’t see detailed segment and chromosome data on Ancestry.

For example, in the image below you can see that the total shared DNA is 50 cMs across one segment (weighted). The unweighted DNA that I share with this match is 52 cMs, which also happens to be the same amount as the length of the longest segment (unweighted).

If your DNA match is a relatively close relative who shares more than 90 centimorgans with you, then you will find that the total shared DNA matches the unweighted DNA. This is because the algorithm that assigns more weight to DNA segments that are likely to be inherited from a recent ancestor (Timber) is not used on DNA matches who share more than 90 cMs.

An example of unweighted shared DNA.  In this case, since the matches are relatively close relatives sharing more than 90 cM, the Timber algorithm is not applied

The DNA match displayed above is a second cousin sharing 368 centimorgans. The unweighted shared DNA is the same as the total shared DNA because the Timber algorithm is not used for close DNA matches because most of the shared DNA segments are likely inherited from the recent common ancestors.

Which is more accurate: Weighted or unweighted shared DNA?

The weighted shared DNA, which is the amount that we see reported on the DNA match profile page, is the most accurate number to use when trying to determine how we are related to a DNA match.


I hope that this post helped you understand more about unweighted shared DNA, including what it is, and how to use the information to research your matches. If you have any questions about something that you read in this post, please feel free to join us in the discussion below.

Thanks for stopping by today!

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Jason Lee

Sunday 17th of April 2022

I haven't seen convincing evidence to support the idea that Timber is a net benefit. There's been no scientific peer review that I'm aware of.


Sunday 20th of March 2022

I just don't understand this at all. I have a 1rst cousin 1 time removed that is showing we only share 46 cM but the unweighted is 73 cM, on 4 segments.


Tuesday 3rd of August 2021

I think this statement is confusing: "We will only notice this phenomenon when we have matches with whom we only share one segment of DNA." Can you go into more detail about this?

My match to a second cousin 1X removed: shared DNA 43 cM across 5 segments, longest segment 20 CM. Unweighted = 60 cM.

My shared segments are 5, not one.

I think what you are saying is in a certain scenario "something" will happen if you share only one segment. But, you are not saying that you will only see a different unweighted value if you only share one segment.

My situation is the same as the first person who posted a comment. There is a difference in shared versus unweighted AND they have 3 segments, not one:

"17 cM across 3 segments; Unweighted shared DNA: 33 cM



Monday 26th of July 2021

Because my biological father’s side chooses not to share family tree because of me being 1/2 sibling.. my dna all appears as unweighted… 1800+cm So “Timber” is very not fair in judgement… my segments are very long.. both 1/2 sibling & her daughter BUT my father was iden twin so my 1st cousin & her daughter run high also… help


Sunday 1st of August 2021

@Kat, By no means am I making light of your situation, I just felt some relief to discover someone else who discovered their bio father is also an identical twin. I do hope you get more positive response from them than I did.


Saturday 3rd of July 2021

I have to say, I don't find the Timber algorithm to be more accurate, or even helpful. What it's done is demote all my third cousins on my Jewish side to distant relations - I could not figure out why I was seeing so many familiar names allocated to the 4th-6th cousin range until I started checking each individual entry. Then I noticed the unweighted total was often more than twice the weighted and the longest segment was usually longer than the weighted total. Thank you for explaining why, but for me it's made a lot more work. I now have to click through all the hundreds of unknown 4th-6th cousins one at a time to check if they are actually worth researching (I am trying to trace all the descendants of one particular couple), instead of being able to quickly surmise this by looking at longest segment vs total cM/segments on the matches list.


Wednesday 27th of July 2022

@ESA, Nobody said being a Jew was easy, eh? ;) But seriously though, it's not fair but it is what it is. I don't know the science behind it but it sticks, the DNA is indestructible! Dad and I are both 2%, and check this out, on ALL of the DNA sites, tons of 100% Jewish matches, and this is the weird part (for someone not familiar with Jewish DNA matching) most of them, Dad and I match EXACTLY the same amount. How is that even possible? It's amazing really. Especially chromosome 1, indestructible, not even a sliver taken from those chunks when I got them from Dad. I had to look up what this unweighted meant and found this blog. Because by chance I clicked on that and saw that one of my matches on Ancestry (she's on 23andme, FTDNA, gedmatch and MyHeritageDNA too) but on Ancestry it says I match her at 25cm, unweighted 40cm longest segment 40 cm. That means 23andme timbers too, they say 36cm on one seg for her. Frustrating, but remember, it is very unique and special. I'm not sure what the scientific explanation is.

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