When we compare your DNA to the DNA of one of your matches, we calculate a confidence score for you. This score lets you know how much DNA evidence there is for you and your match actually being related (see figure 1).
But, just because you and another member have identical DNA doesn’t mean that you both inherited that DNA from a recent genealogical ancestor. (Learn how you can have identical DNA and not be related.) That’s where the confidence score comes in, and how we calculate the likelihood that you and your DNA match are actually related. A high confidence score means that we’re pretty sure that your DNA is identical because it was inherited from a recent ancestor. A lower score means that your identical DNA might be because you’re related, but it might also be because you have similar ethnic or regional backgrounds.
The confidence score is based on the amount and location of the DNA that you share with your match. We show the shared amount using centimorgans (cM), a unit used to measure the length of DNA. The higher the number, the higher the confidence, and in general, the closer the relationship. Since you can share DNA with your match on one or more segments in different locations in the genome, we show you how many. Note that the number of segments and number of centimorgans that we show reflects only those segments that we believe were inherited from a recent common ancestor (in other words, segments that are likely to be identical by descent).
When you’re exploring your list of DNA matches, look for these confidence scores and let them help you focus your research.
|Confidence Score||Approximate amount of shared centimorgans||Likelihood of a single recent common ancestor||Description|
|Extremely High||More than 60||Virtually 100%||You and your match share enough DNA to prove that you’re both descendants of a common ancestor (or couple)--and the connection is recent enough to be conclusive.|
|Very High||45—60||About 99%||You and your match share enough DNA that we’re almost certain you’re both descendants of a recent common ancestor (or couple).|
|High||30—45||About 95%||You and your match share enough DNA that it is likely you’re both descendants of the same common ancestor or couple, but there’s a small chance the common ancestor(s) are quite distant and difficult to identify.|
|Good||16—30||Above 50%||You and your match share some DNA, probably from a recent common ancestor or couple, but the DNA may be from distant ancestors that are difficult to identify.|
|Moderate||6—16||15—50%||You and your match might share DNA because of a recent common ancestor or couple, share DNA from very distant ancestors, or you may not be related.|
The amount of centimorgans you share with a match can also help you understand your relationship to them. For example, you’ll usually share about 120 centimorgans with a 3rd cousin, but it’s possible to share as few as 90 or as many as 200. Be aware that the precise amount of shared DNA can vary beyond the ranges shown in the table below.
|Approximate amount of shared DNA (in centimorgans)||Possible relationship|
|3,475||Parent, child, or identical twin|
|2,400—2,800||Full sibling (including fraternal twins)|
|1,450—2,050||Grandparent, aunt, uncle, half—sibling|
|680—1,150||1st cousin, great—grandparent|
|6—20||Distant cousin: 5th cousin — 8th cousins|