Interpreting matches with low cM values and high SNPs (or vice versa)?

What does matching SNPs mean?

SNPs are locations that are compared to each other to see if mutations have occurred. Think of them as addresses on a street where an expected value occurs. If values at that address are different, then they don’t match. If they are the same, then they do match.

How many centimorgans is a good match?

Centimorgans (cM) are units of genetic linkage between two given individuals. For example, if you share 1800 cM with an individual, that means you share around 25% of your DNA with them. A strong match will have around 200 cM or more.

What does cM mean in DNA results?


A centimorgan (abbreviated as “cM”) describes the length of a piece of DNA. It is a unit of measurement. More specifically, it measures the distance between two chromosome positions. A shared DNA segment is a chunk of genetic material shared between two individuals.

How many centimorgans is significant?

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.
What does the match confidence score mean?

Approximate amount of shared DNA (in centimorgans) Possible relationship
200—620 2nd cousin
90—180 3rd cousin
20—85 4th cousin
6—20 Distant cousin: 5th cousin — 8th cousins

What does total cM mean on GEDmatch?

“Total cM” tells you how much DNA you share with your top matches! A big number means that you are closely related. A smaller number indicates a more distant relationship. The largest number possible in the One-to-many tool (for identical twins, for example) is about 3,500 cM.

How many SNPs is a good match?

700 SNPs

GEDmatch say that “to qualify as a ‘match’ in the genealogical time frame, results must have a largest autosomal segment that has at least 700 SNPs and be at least 7 cM”.

How many centimorgans do 1st cousins share?

You usually share about 850 cM with a first cousin, but that number could be as low as 553 or as high as 1,225 cM. Likewise, a single shared-cM value could indicate a variety of relationships. For example, 1,200 shared cM could indicate a first cousin, great-grandparent, grandparent, or great-niece.

How many cM do full siblings share?

around 3500 centimorgans

The amount shared is usually expressed in something called centimorgans. Full siblings tend to share around 3500 centimorgans while half siblings share closer to 1750.

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