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The 4mm Beard: Exactly What You Need To Know

August 12, 2023
The 4mm Beard: Exactly What You Need To Know

The 4mm beard is an interesting one. Falling well within the range of “heavy stubble”, it has the benefit of being very noticeable while remaining airy and subtle. 

It has several other things going for it, the most important of which would be versatility.

However, longer stubble lengths do come with some additional maintenance requirements that need to be considered. Not much, but certainly some. 

At this length, once again the Philips Norelco Oneblade QP6520/70 is the trimmer that will meet all of your needs – trimming, shaving, and edging. You can find out more on Amazon here. But more on this later. 

This guide will go into more depth about this length than you may have initially expected.

It seems like quite a niche topic, but in-depth is what I like to do. I’ll show you what it actually looks like, how to decide whether it’s the length for you, how to trim it, and more. 

Plus, if you’re interested, click here to check out my most recommended stubble trimming and grooming products of the year.

What Does The 4mm Beard Look Like?

the 4mm beard
From 123rf

The beauty of this length is that it’s very easy to keep neat. Keeping it in check won’t add too much time to your grooming routine at all. 

A carefully sculpted 4mm beard has the benefit of being noticeable. When stubble is particularly short it can sometimes be ignored or even mistaken for non-existent.

This is sometimes the desired outcome – light stubble certainly has subtlety on its side. 

But 4mm worth of facial hair is difficult to ignore. It’s long enough to be considered heavy stubble, yet short enough to not be labeled a “short beard”. 

Although the picture above is of a classic 4mm beard, the length of hair can be sculpted into a variety of different styles. This includes the goatee, the disconnected goatee, the chinstrap, and more. 

That’s one of the benefits of having a longer stubble length – there’s more you can do with it. 

How Long Does It Take To Grow A 4mm Beard?

Around 8 to 9 days. Most men can quite comfortably grow 4mm worth of facial hair within this time period. 

Of course, every man’s rate of growth is different. Some men will take a little longer, and some men even shorter. But on average, 8 to 9 days is a pretty safe bet. 

What I find a little annoying about longer stubble lengths is the fact that messing up your trim is more of a nuisance. 

If you’re trying to trim a new style and mess it up due to the slip of the hand, there’s a chance you’ll have to shave everything off.

You’re then back to square one and have to wait another 8 to 9 days to get your length back. 

This is in contrast with light stubble which is easier to experiment with. If you happen to mess up and shave everything off, you’re back in business in just a couple of days. 

But still, it’s not really a big deal. Ultimately, it’s still just stubble and doesn’t take much to get back. 

Compare this with longer beards having to get trimmed off after getting butchered by a barber. 4mm beards won’t ever give you this much grief.  

Is The 4mm Beard The Length For You?

There are certain factors that need to be taken into account before deciding on a beard length.

Not all of them will be of equal importance to all men. It’s down to personal preference, and that’s one of the beauties of personal grooming. 

Here are a couple of factors to consider. 

1. It can look scruffy when not maintained properly

Although this may seem obvious, men are often oblivious to how scruffy their stubble can look.

This is particularly the case with heavy stubble. It often feels less obvious than it looks. 

When not maintained or groomed properly, it can simply be labeled as untidy or unshaven. This isn’t what we’re going for. 

We’re aiming for carefully sculpted, designer stubble that looks very intentional. Stubble is no longer considered the “lazy man’s beard” which is great. But ultimately, if it isn’t looked after, it will certainly look like one. 

The grooming requirements of a 4mm beard are still minimal. But it does require some. 

Of course, trimming it to a nice, even length, and shaving outside the borders are essential. Having carefully-defined borders is arguably the most specific differentiating factor between designer stubble and untidy stubble. 

I’ll be detailing how exactly you can achieve this later on in the article. 

Other than trimming and shaving, moisturizing is also a crucial component of your grooming regimen.

Beard oil is also worth talking about here. Although it’s definitely more commonly used for longer beards, I’d still recommend using it on heavy stubble. You won’t need much – a single drop per session would do. 

Beard oil can give it a nice, slick shine and can once again make it look more intentional. As is often the case with men’s grooming, it’s the little touches like this that cumulatively make the difference. 

2. It can itch

Heavy stubble can itch. It’s a fairly awkward length in that respect.

One of the benefits of shorter stubble is that it generally isn’t long enough to itch, although it definitely feels rougher to touch. 

Although the itch can be a little noticeable, it generally isn’t bad enough to be considered troublesome at this length. 

Benefits Of The 4mm Beard

There are several, but I’ve narrowed it down to two. Bear in mind, these benefits could be applied to any heavy stubble length. 

1. You can work with it 

In other words, there’s enough hair there to experiment with. One of the disadvantages of short and medium stubble is that the lengths can be difficult to shape.

Shaping and grooming stubble gets easier as it gets longer. 

It’s long enough to try out different shapes and styles. Don’t ever be afraid to experiment with it. That’s part of the fun of having facial hair in the first place. 

It’s also long enough to dye if you wish to do this. Stubble dyeing is becoming increasingly more common as stubble in itself becomes more popular. 

2. It’s pretty soft for stubble

The underlying principle here is that the shorter a strand of hair is, the sharper it’s edge is. 

Short stubble feels a lot like sandpaper, particularly when freshly trimmed. You’ll notice that as it gets longer, even by just a couple of millimeters, it will feel less rough against the skin of your hand as you stroke it. 

Heavy stubble feels softer than light stubble for this very reason.

The first person that will be thanking you for this will be your partner whose face has borne the brunt of sharp stubble more than anyone else. 

Again, it may not be all that important to you. However, it’s just something to bear in mind. 

The Best 4mm Beard Trimmer Out There

Right now, I do feel it’s hard to beat the Philips Norelco Oneblade QP6520/70 when it comes to stubble lengths such as this one.

It meets whatever grooming requirement that comes to mind – trimming, shaving, and edging

Click here to check it out on Amazon.

It gives you very precise control, allowing for 14 length settings up to 10mm. Because it deals pretty exclusively with such short length settings, I’m quite comfortable labeling it a “stubble trimmer”. 

However, allowing you to trim up to lengths of 10mm does open the playing field up to short-bearded men as well. 

It has a very comfortable contouring head allowing you to reach the more difficult areas of a stubble beard. The area immediately beneath the jawline is a common culprit here. 

It’s certainly a trimmer to contend with. 

How To Trim A 4mm Beard Like A Pro

It isn’t hard. I mean seriously, it doesn’t take much. Having a step-by-step routine to follow is important, however. This is the case no matter how simple a grooming habit is. 

Following this will result in a neat, classic, 4mm beard consisting of hair on the chin, cheeks, and mustache. 

As you’ll soon see, defining the borders will be a crucial step you won’t want to miss. 

Step 1. Grow it out for 12 days

This is assuming you’re starting off from a freshly shaven face. If you’ve already got facial hair that’s longer than 4mm, ignore this step and move onto step 2. 

Although the majority of men will reach the 4mm threshold after 8 to 9 days, you’ll want to grow it a couple of millimeters longer than this to start off with.

12 days should be enough time to achieve this for most men. If your growth is a little slower, give it a few more days still. 

The reason you want to delay your trim a little is that you’ll want to trim down to 4mm from a slightly longer length.

6mm worth of facial hair is a perfect point to start with. If you’re already at a longer length, simply trim it all down to around 6mm first. 

Step 2. Trim the whole beard down to 4mm 

This is where your trusted trimmer comes into play. Set its adjustable length to 4mm and start trimming your entire beard – chin, cheeks, mustache, and neck.

You may initially think that trimming everything down to a perfect 4mm will give you the most evenly distributed result – this is incorrect

Facial hair is thinner in parts and thicker in parts. The cheeks are often notoriously thin, whereas the chin and mustache area are often thicker. 

To account for this, try varying the length by a millimeter or half a millimeter here and there. Trim the thicker areas just a tiny bit shorter than the thinner areas. 

Funnily enough, this will actually make the entire stubble beard look more even. This is despite some parts being 4mm, some being 3.5m, and some being 3mm. 

Step 3. Define your stubble borders

It’s time to define the neckline and cheek line of your 4mm beard. Doing so is crucial in ensuring your stubble looks intentional and not accidental. 

The neckline is the border between the hair on your neck and your neck skin. It can be tricky to get right but is integral to an effective stubble beard.

This is because a bad neckline is very obvious at such a short beard length. Set it too high and it can produce a double-chin effect. Set it too low and it just looks incredibly untidy. 

Visualize a curved line running from ear-to-ear across your neck. The midpoint of this line should lie two finger-widths above your Adam’s Apple.

It should also slant upwards on each side so that it almost follows the angle of your jawline. 

Trim this line using the naked blade of your trimmer, as well as all of the stubble that lies beneath it. You’ve just trimmed one solid neckline indeed. 

Trimming your cheek line is a little more simple. Some cheek lines are straight, and others are curved.

You should be able to make out your natural cheek line – the best course of action would be to simply accentuate this. 

Again, using the naked blade of your trimmer, trim any stray hairs that lie above your cheek line. 

Step 4. Shave

The naked blade of your trimmer can only trim so short. It will still leave some stubble, as short as it may be.

Most of these trimmers can usually trim down to around 0.4mm. Although this may seem very short, it’s still long enough to see and feel. 

To get the smoothest results, you’ll want to shave the areas outside your stubble beard borders. In other words, above your cheek line and below your neckline. 


There you have it. You’ve learned what it is, what it looks like, and how to achieve it like a consummate professional. 

Hopefully, that was as in-depth as you needed it to be. Heavy stubble can look glorious when groomed correctly. It’s also such a fun length to experiment with.