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You probably got here from this page. If not, it’s probably a good idea to go look at it and see what this page is about before continuing.

Many of the statistics here won’t actually be viewable at AncestryDNA. The real purpose of this page is to provide the most accurate possible centiMorgan values for given relationships based on an AncestryDNA upload to GEDmatch. If you aren’t analyzing an AncestryDNA kit at GEDmatch for the purposes of investigating possible incest, you’ve probably come to the wrong page. Although, you could use comparisons from AncestryDNA and only compare them to the HIR values in Tables 2-4 below.

Expected cM of ROH for an AncestryDNA kit at GEDmatch

Table 1. ROH in cM for a given scenario. The number of cM that would be reported for a given scenario at the GEDmatch AYPR tool when using a kit uploaded from AncestryDNA. None of these statistics can be viewed at AncestryDNA. One must first upload their AncestryDNA kit to GEDmatch.

Table 2. Shared cM with various relatives when your father is your mother’s son (mother is also paternal grandmother). Any of the rows labeled HIR + FIR or simply FIR are only for AncestryDNA kits uploaded to GEDmatch, since AncestryDNA counts FIR segments as if they’re HIR segments. Rows with HIR only or no designation are valid for comparison directly on Ancestry’s site.

Table 3Shared cM with various relatives when your father is your mother’s brother (mother is also paternal aunt). Any of the rows labeled HIR + FIR or simply FIR are only for AncestryDNA kits uploaded to GEDmatch, since AncestryDNA counts FIR segments as if they’re HIR segments. Rows with HIR only or no designation are valid for comparison directly on Ancestry’s site.

Table 4Shared cM with various relatives when your father is your mother’s father (mother is also sister). Any of the rows labeled HIR + FIR or simply FIR are only for AncestryDNA kits uploaded to GEDmatch, since AncestryDNA counts FIR segments as if they’re HIR segments. Rows with HIR only or no designation are valid for comparison directly on Ancestry’s site.

Feel free to ask me about modeling & simulation, genetic genealogy, or genealogical research. To see my articles on Medium, click here. And try out a nifty calculator that’s based on the first of my three genetic models. It lets you find the amount of an ancestor’s DNA you have when combined with various relatives. And most importantly, check out these ranges of shared DNA percentages or shared centiMorgans, which are the only published values that match known standard deviations.