Thinning Shears and the Number of Teeth

Thinning shears
Thinning shears - Photo: MsMaria/Shutterstock
Q: I'd like to purchase a pair of thinning scissors for slightly thinning the hair on the top of my wife's head. When I look on the web, I see some have as few as 20 teeth and some have as many as 45 teeth and some have teeth on one blade, while others have teeth on both blades.
Some advertisements for thinning shears show as much as 50% hair being removed while others show as little as 15%. Please help me to understand what I need to know to buy the right thinning shears.

A: This is generally the number one problem people face when looking at thinning shears. The fact that the way they work seems counter-intuitive. You see, the more teeth a pair of thinning shears has, the less hair is removed, while those shears that have fewer, wider and more widely spaced teeth remove more hair and in chunks.
The percentages listed with a pair of thinning shears description are an approximate percentage of hairs that are cut with each closure of the blades on a slice of hair.
So those shears that list 15% removal will take away about 15% of the hair between the blade in one snip, and additional 15% increments with multiple snips. Because of this, even with smaller percentages, you want to make sure that you don't overdo it with the shears, or you can really make some significant hair removal.
The higher tooth count shears are generally used for blending and removing bulk from hairstyles - particularly with fine-to-medium, straight-to-wavy hair types. These are probably what you want. I would actually opt for the shears that remove about 15% of the hair per pass since you can always remove a little more, but you can't add it back in once it's cut.
The smaller-number/wider-teeth shears are meant for curly hair types as they can remove chunks of curl and leave the hair looking lighter and less bulky without making it so diffuse. Using these kinds of shears on straighter hair types will result in a choppy, gapped look and is generally not desired.

So remember, when it comes to thinning shears: More removes less and less removes more.
See also:
How to use thinning shears
What's a good number of teeth in one sided thinning shears to avoid thinning the hair too much?
What is the purpose of thinning shears with double rows of teeth?
What size scissors are best for a beginner?