Hair Thickness Chart, Types & Measurement - Hair Thickness vs Hair Density

Many people mix up hair thickness and density. When some say they have thin hair, this might mean thin thickness or low density. How to distinguish them and figure out the meaning of these common terms in the hair industry? In this article, we’ll explain each type of hair thickness and the difference between hair density and thickness.

What Is Hair Thickness?

Hair thickness refers to how wide or thick each strand of hair is. Holding a single strand of hair between your fingers. If you barely feel it, your hair is probably fine or thin hair. But if you can clearly feel the strand and it feels strong or wide, your hair is medium or thick. This simple touch test helps people figure out their hair thickness without any special tools.

Genetics plays a big role in determining your hair thickness, which means it often runs in families. Some people naturally have wispy, soft strands, while others have hair that feels rougher or drier because their strands are thicker. Hair thickness also changes as people get older. Hair usually reaches its fullest amount by around age 35, but after that, it starts to thin. By age 45, people often lose about 5% of their hair, and by 50, around 11%. Men and women experience this differently: men tend to lose hair, especially at the crown or hairline, while women usually have thinning all over their scalp without the hairline moving back.

The diameter of hair affects not just how hair looks but also its strength and flexibility. Thicker strands have more of the protein that makes hair strong, so they are tougher and more flexible. Thinner strands are more fragile and less flexible, which means they can break more easily.

How Is Hair Thickness Measured?

The thickness of hair strands is usually measured in millimeters. On average, a single hair strand is about 0.03 to 0.06 millimeters wide. Some people’s hair strands can be even thicker, reaching up to 0.2 millimeters. When strands are closer to the thinner end, they’re called fine hair, and when they are on the wider end, they are called thick or coarse hair.

Hair Thickness Chart & Types

Fine Hair

Fine hair consists of very thin strands, about half as wide as a sheet of printer paper. Each strand has a small diameter and is made up of just two layers: the cortex and the cuticle. Because fine hair has less protein inside, it feels soft, silky, and delicate. This makes it fragile and more likely to break if handled roughly. Fine hair can get oily quickly and often struggles to hold styles for long. People with fine hair usually need products that add volume without weighing their hair down. The upside is that fine hair is often more flexible when it comes to coloring and styling, but it still requires gentle care to avoid damage.

Is fine hair the same as thin hair?

Not. Thin hair and fine hair are different. A more common viewpoint is that fine hair refers to the smallest hair thickness, while thin hair indicates low density.  

Medium Hair

Medium hair is the most common type and falls right in the middle between fine and coarse hair. Its strands are thicker than fine hair but not as thick as coarse hair, making it stronger and better at holding hairstyles. Medium hair looks fuller and is less likely to break, but it doesn’t always react well to chemical treatments like coloring. It can also be prone to frizz, especially in humid weather. When choosing products for medium hair, it’s important to pick ones that help control frizz and keep the hair smooth without making it heavy.

Coarse Hair

Coarse hair features the thickest strands, about twice as wide as fine hair. Unlike fine hair, coarse hair has three layers: cortex, cuticle, and medulla, which makes it stronger and more full-bodied. This extra layer adds protein and gives coarse hair a heavy, thicker feel. Coarse hair is more durable and can handle heat styling, coloring, and chemical treatments much better than finer hair. However, it takes longer to dry and tends to frizz easily, especially in humid weather. People with coarse hair often enjoy styles that stay put longer but may need special care to keep their hair smooth and manageable.

Hair Thickness vs Hair Density

It’s important to know that hair thickness is different from hair density. Hair thickness and density do not always correlate. It’s possible to have thin hair that occurs in very high density. Conversely, someone may have thick individual hairs but low density.

1. Definition and Measurement

Hair thickness refers to the width or diameter of an individual hair strand. It is a physical measurement, often expressed in microns or millimeters, where fine hair is typically around 50 microns thick, and coarse hair can be as thick as 120 microns. But hair density is about quantity; it describes how many hair strands grow per square inch of scalp, it counts the overall number of strands on the head.

2. Visual and Tactile Appearance

Thicker hair strands tend to feel more substantial and can appear stronger or coarser to the touch, whereas finer strands feel more delicate or wispy. Density, on the other hand, impacts how full or voluminous hair looks. High-density hair appears lush and thick overall because there are many strands packed closely together, while low-density hair may look sparse or thin despite the thickness of individual hairs.

3. Genetic and Structural Factors

Genetics largely determines both hair thickness and density, but each follows a different pattern. Thickness depends on the shape and size of the hair follicle producing each strand, while density depends on the total number of hair follicles present on the scalp. Hormonal changes or aging may affect thickness by shrinking hair strand diameter, but they may not necessarily reduce the number of hairs, thereby affecting thickness and density differently over time.

4. Practical Testing Methods

To test hair thickness, one can compare a single strand against a sewing thread or roll a strand between fingers to feel it. For density, methods include observing scalp visibility; if the scalp is easily seen through the hair, density is low; if it’s difficult to see the scalp, density is high. Another practical test is measuring the circumference of a ponytail: a larger circumference indicates higher density, while thickness requires an individual strand comparison.

5. Impact on Hair Care and Styling

Hair thickness influences how hair responds to styling and product use. Thick strands allow for more treatment and styling versatility. Fine hair requires gentler care and lighter products. And high-density hair may need sectioning for easier detangling and styling, whereas low-density hair benefits from volumizing techniques to create the appearance of fullness.