Will my mustache fill in? [SOLVED with science]

The great thing about a mustache is that it very quickly goes from looking patchy to full and thick. However, in the early stages of growth it can be really difficult to see the full potential of your mustache because you may be in the early stages of puberty – whether hair isn’t as fully developed – or you might have light hair or a low hair density. The good thing is that there are plenty of options for you and it may only require a little bit of patience to achieve the mustache of your dreams.

It is likely that your mustache will fill in as you grow older and you decide to let the hairs grow longer. It will take about a month before it starts to look full and thick. If you have low hair density you can use minoxidil to encourage vellus mustache hairs to turn into terminal hairs.

Growing a mustache is one of the simplest things that you can do to change your facial hair style without having to commit to the long and arduous journey of growing a full beard.

Most people see significant improvement in their mustache in the first couple of months of growth and if you want to know more about how long it takes to grow different types of mustaches – stubble through to full and fancy check out my other article where I have calculated how long it takes to grow each type of mustache. Click here to be taken to article.

There are plenty of reasons why your mustache will not filling – it may be that you are simply judging your mustache too early, your genetics may be hindering you, you may have light hair or very low hair density. Whatever it is we should take a look at each of these and the solutions for overcoming each type of issue.

Why can’t you grow a full mustache?

In this section we are going to take a look at why you probably can’t grow a full mustache or, at least you don’t think you can.

You are young

Many people are judging their mustache is far too early in their beard growing journey.

I think a lot of people think that beard and mustache growing is something that happens as soon as puberty and starts. However, testosterone causes a number of effects on the body and growing a thick beard or mustache is one of the last changes to occur during puberty.

It could be that you are simply judging your mustache far too early.

Even though there is a significant amount of science and data around when puberty starts. There isn’t much data on the other end of the beard growing spectrum. We are limited to forum posts and answers from anonymous users of different websites to try to get a grasp on what is a typical age at which a beard stops filling in.

I took a look at the most popular sites online where people freely share personal information. This included Reddit, capital, and Quora where people as a very similar question. I created a series of different age ranges and tallied the responses from the different websites.

Here is the result of going through all of the forums and noting down at what age people said their beard stop filling in. Here is a graph which shows the distribution of responses to a question about what age people’s beard stop filling in.

You can see that the majority of people noticed that their beard stopped filling in at the ages of 21 to 25 – 32% of people who responded.

If you are younger than 25 it is likely you still got a fair amount of growth left in your beard. Personally, I found that my dear continue to grow well into my 30s and, based on the graph above, about 21% of people also noticed that there beard continue to grow up until the age of 30.

A little bit of patience goes a long way in the beard and mustache growing world. Your journey will be unique to you and you shouldn’t wish to rush it.

Your genetics may hinder you

Genetics plays a huge role in determining whether or not you can grow a beard and mustache.

You can get an indication of whether or not you can grow a beard by looking at your family and heritage.

The likelihood that you would be able to grow a beard. You may be in a family where many people grow thick beards and mustaches that you may not be able to. That is just the luck of the genetic draw.

A recent study published in 2010, they found that black boys developed secondary sex characteristics about seven months earlier than Caucasian boys. This demonstrates the difference between the genetics of different nationalities which could indicate why we see a significant difference in the production of a beard between people of different races.

We even get a very small amount of genes from even more distant relatives. You share about 0.78% of your DNA with your great-great-great-great-great grandfather (aka 5th great-grandfather). So, even though it is very unlikely that your beard growing potential comes from your great-great-great-great-great grandfather – it is a possibility.

People with Asian heritage also struggle to develop thick, dark mustache hairs. This is purely due to the evolutionary direction of people in that race. On the other side of the coin, people with Arab and Greek or Mediterranean heritage can typically grow great beards and mustaches which are thick and full.

Light hair

If you have particularly light hair your beard may look as if it has gaps when it doesn’t.

Light blonde mustache hairs can easily make a mustache look less full and patchy. Light hair is much harder to grow out to cover gaps.

If you have light hair on your mustache you have the opportunity to die it’s a darker colour or simply wait for it to get much longer.

Low hair density

Another important question to ask yourself to determine whether or not your beard has potential is to look at the density of your beard hairs.

The density of your hair placement will also determine a thick your beard and mustache looks when it has grown.

A 2011 study found that you can reliably determine the density of a beard and mustache by using a simple photographic method. Take a look at the image from the University of Pennsylvania for examples of the hair density that they found.

Having a low hair density can be improved with temporary beard thickeners such as beard hair fibers and a beard pen. For a more permanent solution you should try using minoxidil to encourage the light, vellus hairs to turn into thick terminal hairs.

If you want to be sure that you can grow a beard here are the four signs that your mustache will fill in.

Signs your mustache will fill in

In the early stages of growing mustache all you need is hope and some faith that eventually your mustache will become the mustache of your dreams.

When I was growing a mustache in the early stages of my beard growth journey it seemed to take forever to go from the awkward patchy phase to growth density and thickness that I was happy with.

Here is what you should look at if you want some indications that your mustache will turn into a mustache that you can be proud of.

Rate of change

You should look at the rate of change of your mustache. That is, the rate of white hairs turning into dark and thick terminal hairs.

One of the easiest ways to check that your mustache is heading in the right direction is to take a photograph of your mustache every week and create a slideshow for comparison between weeks.

I know that when I look back of photographs I’m always amazed at how much my beard and mustache grown – even though I do not notice its daily progression.

When a man strikes puberty the testosterone and its metabolised version, DHT, floods through the body. When it reaches a hair follicle which has androgen (sex hormone) receptors it can turn a white and transparent hair – known as vellus hair – into a thick terminal hair.

The growth cycle of vellus hair to terminal hair follows the following path:

  • Lanugo – this type of hair is first produced by beetle hair follicles and is present on the foetus from about 16 weeks of gestation up to 33 weeks until birth.
  • Vellus – the less hair replaces the previous type of hair and is present in children and adults. It is an essential part of controlling your temperature as well as providing sensory input for detecting and sensing 3D space around you.
  • Terminal – vellus hairs can turn into terminal hairs once they have reached puberty. The notable change is that vellus hair is stronger, longer, and more noticeable due to its thickness.

This transition occurs because some parts of your body have receptors which respond to testosterone and its derivatives such as DHT. A study published in 2008 goes through the effect of these hormones and hair growth.

As long as the hairs on your face are continually turning from white hairs to terminal back hairs you can be sure that your mustache still is growing into its full potential.

High density

You can also be assured that your mustache is growing into its full potential if you notice a high density of hairs across your entire upper lip.

Having a high density combined with a high coverage of hairs on your upper lip that you notice are turning steadily from white to black should also fill you with hope.

During my mustache growing journey – in the later stages of puberty I notice that the corners of my mustache were turning dark before migrating to the middle of the face.

If you do not have a high density of mustache hairs you can simply use minoxidil or a temporary beard darkening and thickening solution such as hair fibres.

It is much harder to cover up areas of low density growth on your top lip than it is to cover up patchy areas your beard. Because there is much less hair around you will not be able to style the hair over the gaps as easily.

However, with a little bit of mustache wax and beard bar you may be able to cover the weak areas of growth.

Early stages of puberty

If you have only recently gone through puberty you may have much more beard growing potential left than you think.

When I was a teenager I was certainly very impatient with the growth of my beard but it very quickly developed.

Because there is a huge range of when people actually go through puberty there is also a large range of when men can expect their beards to become fully developed. A scientific study published in 1980, looked at the normal ages of pubertal events among American males and females.

The study looked at 36 males and 18 females which were examined at six-month intervals during a five year period.

They found that the median age at which men developed facial hair was at the age of 15 years old. 20% of the boys investigated had facial hair at the age of 13. Whereas by the age of about 16, 95% of the men had facial hair.

Considering that this is the onset of a beard growth in males it is clear that there is plenty of opportunity in future years for your beard to become thicker and fuller. I discussed my beard growth journey from the ages of 17 through to 35 in a YouTube video, below.

Just give your mustache some time to fill in before you jump into any significant intervention.

Other people in your family

Like I said above, looking at your genetics and the males in your family you have got a mustache and beard may give you an indication of the sorts of potential your mustache and beard may have.

This is not foolproof as it depends on the genetic lottery of genes that you have inherited from your mother and your father.

If the men in your family – both the males on your mother and father’s side – can grow a good thick mustache you have reason to be hopeful that your mustache will continue to grow into a thick and full bushy mustache.

There are a few things that you can do to help your mustache fill in if you feel like you need a little bit of an extra boost.

What you can do to fill in a mustache

Here are the things you can do to help your mustache fill in.

Wait 3 months

Before judging your beard and mustache allow it to grow for three months. There is an ongoing joke on my YouTube channel where I say that this is the solution to the majority of beard and mustache growing problems.

However, I still think that this is very true.

How long does it take for a mustache to fill in?

After approximately three months of growth your mustache should be approximately 1 ½ inches long. If you want to know how long it takes to grow mustache check out my other article – click here where I have given you the data. Also if you want to low how to grow a mustache quickly you should check out my other article where I go through the insider tricks for making your mustache grow effortlessly quick.

Use minoxidil

Minoxidil was first introduced as an oral medicine for the treatment of hypertension in the 1970s. At the same time doctors observed that there was hair regrowth in bolding patients which led to the development of topical formulation for treating male pattern baldness in males and then females. There was a 2% minoxidil solution launched on the market in 1986 followed by a 5% solution in 1993. It has continued to be a good topical treatment for a range of hair related disorders.

The most well-known hair growth treatment is Minoxidil. It’s found in hair regrowth products such as Rogaine. The FDA has NOT approved Minoxidil for use on the face and so all of the instructions are for the scalp. One of my favourite places on the internet, Reddit, has a subreddit where people show their progress pics.

Although minoxidil has been used for treating hair loss for a long time it has been proven to provide remarkable benefits to patients with a range of hair related disorders. There are many off label uses for minoxidil that are not currently improved by the FDA even though topical minoxidil treatment is considered an effective and safe options or a range of patients.

Use temporary treatments

If you don’t want to use minoxidil you can look at some other temporary treatments which will make your mustache look fuller and thicker immediately.

Beard pen

Beard pens do exactly what a sound like – they allow you to draw in hairs so that your beard looks fuller and darker. Beard pencils come with different types of tips from a typical pen tip to one with a micro fork. This micro fork allows you to apply more product to your face in a shorter period of time. The Beard filler is designed to reduce the appearance of gaps in your Beard, mustache, and eyebrows.

It’s as easy as using a pen and it lasts all day. The long-lasting formula of many Beard pen and pencils allows you to wear the product for up to 24 hours and many of them are sweat proof and water resistant. This means that if you get caught in the odd shower or you sweat a little bit through the day it will be likely to stay in place.

Using a brush after application will soften the lines that you have just drawn into your Beard and evenly distribute the product throughout your Beard so that there are no harsh gradients or lines for people to pick up on.

Beard fibers

You can also consider applying some hair fibers to the hairs that already exist on your face. There are products such as Toppik hair fibers.

Hair building fibers can either be applied by shaking the hairs over the surface of the beard or you can use a spray applicator attachment. Shaking the hair building fibres are later coverage over a large area but if you want more precise application then go with the applicator attachment. This simply provides a puff of air to deliver the hair fibres.


In this article, we have answered the question: Will my mustache fill in? We have gone through all of the most important things that dictates whether or not your Beard looks full and some of the solutions for each of the common reasons a mustache does not look thick and full.

Patients and using the correct products can help you obtain the mustache of your dreams and many people judge them mustache far too early in the early to mid stages of puberty. Your mustache may continue to grow for many years up until your 40s in some cases.

So, yes your mustache has plenty of potential and time to fill in.

The Author

Andy Stapleton

Andy is a writer and YouTuber with a PhD in science. He has written and/or produced videos for Science Alert, COSMOS magazine, and Australia's Science Channel among others. He is an avid beard grower and after many years of growing and trialling different beard styles, he started this blog to share the tips, tricks, and science that he has learned along the way!