Norwood and Ludwig scales: How are the stages of hair loss classified?

What is a hair loss scale for?

A hair loss scale is a classification that names the pattern of hair loss and how far it has progressed by comparing it with a series of drawings or descriptions. The appearance of the scalp is matched to the closest stage on the scale, so a short, shared term can be used instead of a long description.

Scales are used mostly for androgenetic alopecia (hair loss linked to genetic predisposition and hormones). In most people, this type of hair loss follows a recognizable pattern; a scale gives that pattern a name and makes it easier to track changes over time. We explain how male pattern hair loss develops in our article on male pattern hair loss.

Not all hair loss fits a scale. Hair that falls out in patches or over a wide area within a short time, and hair loss that comes with itching, redness or flaking, may point to other causes. In that case, what matters is finding the cause, not the stage; we recommend seeing a dermatologist for a diagnosis.

The Hamilton-Norwood scale: seven stages in men

The most widely used classification for male pattern hair loss is the Hamilton-Norwood scale, usually called the Norwood scale for short. It is named after Hamilton, who proposed a classification in the early 1950s, and Norwood, who expanded it in the 1970s. The scale tracks hair loss in two areas: the front hairline and temples (the frontotemporal area) and the crown (the vertex).

In reality, hair loss is not always as regular as in the drawings; patterns that fall between two stages are common. In many men, the hairline also moves back slightly at the temples after puberty; this is called hairline maturation. It is not always easy to tell in a single examination whether this is the beginning of progressive hair loss.

Type A, and hair loss that does not fit the scale

In some men, hair loss does not start separately at the temples and the crown. The whole front hairline moves back together, as one line; no island of hair is left extending forward in the middle, and no separate bare patch forms at the crown. Norwood set this pattern apart from the main stages and named it IIa, IIIa, IVa and Va.

As the hair loss progresses, the bare area extends from the front toward the crown. Type A is less common than the pattern described by the main stages; with this pattern, planning often focuses on the front and the hairline.

In other men, thinning spreads over the top of the head without following a clear pattern, sometimes also to the back and sides. This picture does not fit the Norwood scale, and if the donor area (the back and sides of the head, where we take the hair follicles for the transplant) is also thinning, a transplant is often not a suitable option.

Scales used for women: Ludwig, Savin and Sinclair

In women, the hairline often stays where it is; the hair thins over a wide area, especially at the crown and around the part. Because the Norwood scale does not describe this picture well, women are assessed with separate scales that look at how pronounced the thinning is.

In some women, the thinning is more marked at the front and widens toward the forehead along the part; because of its shape, this is known as the “Christmas tree” pattern. Some women also have recession at the temples similar to the male pattern; these patterns may not fully fit the scales used for women.

In women, thinning may not have a single cause; conditions such as thyroid problems or iron deficiency can also contribute, and a scale does not show these. We describe the features of female pattern hair loss in our article on female pattern hair loss, and the situations in which we consider a transplant on our hair transplant for women page.

The BASP classification: hairline and density together

BASP is a classification proposed in the 2000s to describe male and female pattern hair loss in a single system. Its name stands for “basic and specific.” The basic type describes the shape of the front hairline, and the specific type describes the density on top of the head and at the crown:

• L: There is no recession at the front hairline.
• M: The temples have receded more than the middle of the hairline; the line looks like the letter M.
• C: The middle of the hairline has receded more than the temples; the line curves like the letter C.
• U: The hairline has receded back past the crown as well; the remaining hair forms a horseshoe shape.
• F: Diffuse thinning on top of the head, regardless of the front hairline.
• V: Thinning that is most noticeable at the crown.

The number next to the letter shows how advanced the finding is. The result is written as one basic type, followed by specific types where needed; for example, a result such as “M2V1” means that recession at the temples and thinning at the crown are both present, and the numbers indicate the degree of each.

This also makes it possible to describe a man whose hairline stays in place while the top of his head thins; in everyday practice, however, BASP is not as widely used as the Norwood scale.

What does a scale not show?

A scale summarizes how the hair loss looks today; a transplant plan, however, also relies on information that the scale does not show:

• It does not show the donor area. Scales look at the thinning area; they do not tell you how much healthy hair there is at the back and sides. Two people at the same stage can have very different donor areas.
• It does not show the quality of the hair. The thickness and curl of the hairs, and the contrast between your hair color and skin color, affect how much coverage the same number of hairs will appear to give.
• It does not measure how much the hair follicles have shrunk. Hairs that have shrunk (miniaturized) but are still there can make an area look fuller than it is; some of these hairs may become even thinner or fall out over time.
• It does not show speed. How quickly the hair loss is progressing only becomes clear through comparisons over time.
• It can vary depending on who does the assessment. Lighting, the length of the hair, the way it is combed and the person doing the assessment can all lead to the same picture being placed in different stages.

That is why an advanced stage does not, on its own, mean that a transplant cannot be done, and an early stage does not mean that a transplant is suitable. Online tables and calculators that suggest a number of grafts by stage (a graft is a group of hair follicles transplanted together) can give a rough idea, but they are no substitute for personal planning. We do not give a fixed number of grafts in advance; we determine the number you need during the examination, as we make the plan. We explain what determines the number of grafts in our article on how many grafts are needed.

What do we not know yet?

There is no method that can say for certain in advance at which stage hair loss will stop; family history and the age at which hair loss started only give an indication. The scales are based on observations in particular populations; the pattern of hair loss can differ in people of different ethnic backgrounds. None of them measures hair density in numbers; they are all visual comparisons.

How do we use the scale during the examination?

During the examination, we describe the pattern of your hair loss using a scale; this makes it easier to compare changes at follow-up appointments. The transplant plan, however, also relies on the following:

• Hair density in the donor area, and whether there are any signs of thinning there
• The thickness and curl of your hair, and any thinned hair in the recipient area; examining the scalp with a magnifying device (trichoscopy) can help us see these
• Your age, family history, when the hair loss started, how it has progressed and whether it has another cause
• Your expectations and the areas you want to prioritize

As the bare area grows, the balance between the number of grafts your donor area can provide and the area you want covered becomes more important; in advanced stages, it is often not possible to cover every area with the same density. We decide on the priority areas together with you. We explain why the donor area is a limited resource in our article on the donor area and donor dominance.

A transplant does not stop the loss of your own hair in areas that were not transplanted; this hair loss may progress over time. Medications that aim to slow the progression of hair loss may also be part of the plan. Your doctor assesses whether they are suitable for you; we advise you not to start taking any medication on your own.

Whether you are suitable for a hair transplant is determined during the examination, and results vary from person to person.