Use WATO to Explore DNA Match Relationships

Diahan Southard

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Not sure how you are related to your DNA match? Use the free “What Are the Odds?” WATO tool at DNA Painter to explore the possibilities and to help build a more accurate family tree.

If you want to explore and compare different possibilities for how you might be related to your DNA matches, I recommend the What Are the Odds (WATO) tool on the DNA Painter website. Here’s how to use it.

WATO: What Are the Odds for DNA Matches

WATO is a free tool that lets you draw a pedigree chart DNA matches who seem to all share a common ancestor with each other, including the amount of DNA they share with you. It was created by my genius friends Jonny Perl, whom we interviewed about the traits feature he added to DNA Painter, and Leah Larkin, who blogs over at The DNA Geek.

You can then add yourself to their tree in hypothetical locations where you might belong. The tool will tell you if your hypothesis is genetically possible and how likely it is that one of your hypothetical relationships is better than another.

How to use WATO

Let’s use the example of Mandy, who is adopted. She has 3 close DNA matches who also match each other: Donna, Jenna and Portia (all names have been changed for privacy protection). The question is how Mandy fits into their family tree.

Donna, Jenna and Portia were kind enough to include family trees with their DNA test results, so Mandy can construct a family tree that shows how they’re related to each other. Then she can add several guesses about her place on this tree, which are showing up below as numbered hypotheses. She does this with the WATO tool, which looks like this:

WATO What Are the Odds DNA Painter Jonny Perl DNA matches relationships.png

  1. Mandy started by entering placeholder names for the ancestral couple shared by her matches.
  2. Next, she added their known children, Bettina, Lorilynn and Adam, by hovering over the “Grandpa & Grandma” box and selecting the option to add a child.
  3. She kept going with this process until she added each person to the tree that’s needed to reconstruct her relationships to DNA matches. Then, for each DNA match, she hovered over the name to select “Edit Match cM.” She entered the amount of shared centimorgans between this match and herself.
  4. Then Mandy added herself. Her theory was that she was the child of Bettina, which two of her matches had agreed was a possibility. She hovered over her name and selected “Use as Hypothesis” so the system would know to compare all of the centimorgan numbers in relationship to this place on the tree. Then a score showed up for that hypothesis. The score is not meaningful yet, except (because it’s green) to confirm that the DNA that Mandy shares with these matches fits with the genealogical relationship we have assigned to them.
  5. One of the nice things about the WATO tool is that it encourages you to explore other genealogical explanations for your genetic relationships. (This helps prevent confirmation bias.) When you enter more possibilities, WATO gives you feedback on how likely one competing hypotheses is over another. The feedback it gives you is about the odds: which of your hypotheses is more likely? So it requires more than one option. Mandy entered a second hypothesis that would make her a previously unknown half-sister to the parents of Jenna and Donna. Hovering over the name of Hypothesis #2 allowed her to select an option to define her relationships to those siblings as half-siblings. That’s what those dotted lines mean.
  6. Once she added the second hypothesis, the WATO tool gave it a score: 0 (in RED, no less!). This means the suggested place on the tree isn’t genetically possible, given the amount of DNA she shares with each person.
  7. Mandy considered a new scenario: that her birth parent was one of the grandparents. After adding herself there as Hypothesis #3, she hovered over it and indicated a half-sibling relationship to all those siblings.

Surprise! That hypothesis scored a 24! That means this relationship is 24 times more likely to be accurate than her original scenario. But that still does not make it THE right answer. It just makes it the first place we look for documents to support this connection. So, Mandy’s now going back into those grandparents’ lives, looking for evidence that she is connected to one—but not both—of them.

Try it for yourself: the free WATO tool on the DNA Painter website.

WATO Course

If you want even more features with WATO, check out WATO plus.

And if you are still looking to master WATO, check out our on-demand WATO Course, which offers video tutorials, exercises with case studies, and more!

Learn to Work with Your DNA Matches and Mysteries

Ready to start figuring out who your mystery matches are? Take a look at our free guide, 4 Next Steps for Your DNA. We’ve put together all our best tips on how to get started once you’ve gotten your DNA results.

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<a href="" target="_self">Diahan Southard</a>

Diahan Southard

As founder and CEO of Your DNA Guide, Diahan Southard has been teaching people how to find family history answers in their DNA for several years, and she's been in the genetic genealogy field since its infancy. Diahan teaches internationally, writes for popular magazines, consults with leading testing companies, is author of Your DNA Guide–The Book, and producer of Your DNA Guide–the Academy, an online learning experience.


  1. Sue

    Very clear example. Thank you.

  2. Hal

    Thanks for sharing. This tool may have been updated since the article was written. One of the more powerful features is the one that suggests all valid hypotheses. By cM match alone, this suggests three hypotheses at the “strongest” level with a score of 24:

    -You are the parent of Grandpa and Grandma?
    -You are a full sibling of Grandpa and Grandma?
    -You are a half-sibling of Lorilynn, Adam, and Bettina?

    The two additional hypotheses may be ridiculous based upon age, but sometimes those automatically generated hypotheses are gold! It’s a very nice feature.

    • Diahan Southard

      Agreed! It is so nice to have the possible relationships generated for you, and then you can investigate to see which one makes the most sense based on your records.

  3. Lillie Forbes

    WOW! Diahan, using your example above, this is the first time that I get the WATO tool. Thank you!

  4. Darlene Stover

    Just watched your Oct video with Johnny Perl. Great video! This explanation has inspired me to go back and try it again. I’ve been an amateur search angel to a good friend who was adopted. I think I might understand how to use this tool. Thanks!

  5. Carolynn

    Why are Bettina’s, Lorilynn’s, and Adam’s lines leading to Grandpa and Grandma dotted? Doesn’t that indicate half-relationships and wouldn’t that affect the odds of the hypotheses, including among Jenna, Donna and Portia?

    • Diahan Southard

      Yes, the dotted lines indicate half-relationships. In the article it explains more about what the dotted lines mean and when to use them.


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