The 9mm Haircut: Guard, Length, Trim Guide [With Photos]

The great thing about super-short hair lengths is that they take the stress out of styling. It may not be for everyone, but you have to admit the trend is gaining steam. You’re about to learn everything you need to know about the 9mm haircut. 

It’s short. But not so short that it draws attention. The hair is clearly visible and feels soft to the touch, while still being easy to maintain. 

It isn’t so short that you’ll need to do touch-up trims every few days. You could comfortably give it some time before going back at it. 

You need to know what to use to trim it, what it looks like, and what technique you should use for your DIY trims. 

It isn’t complicated, but to get the best results each and every time, you’ll need to have a vague idea of what to expect and how to pull it off. 

Let’s get to it. 

Which Clipper Guard Number For A 9mm Haircut?  

To trim a 9mm haircut you’ll need to use a #3 clipper guard. This will trim down to ⅜ inch. 

Although this more accurately amounts to approximately 9.5mm, for our purposes, it’s (almost) exactly what we need. 

When the hair is this long, 0.5mm here or there really doesn’t make much difference and isn’t noticeable. 

The beauty of it is that most affordable DIY clippers on the market will come with a number 3 clipper guard. You won’t need to buy additional clipper guards or have to look very hard for a clipper that comes with one. 

The main decision you’ll need to make is whether you’re going to go for a 9mm haircut “all over” or add some contrast. 

It’s very common to trim the sides and back down a grade shorter than the top. In this instance, the top would be left at 9mm (#3), and the sides/back would be trimmed down to 6mm (#2). 

This is also very easy to DIY. Trimming the sides down a little shorter than the top does usually make the face look slimmer and the jawline more defined when looking from front-on. 

Of course, a barber could provide fancier forms of contrast such as fades, undercuts, etc. 

But if you wanted to DIY, you can still add some contrast without needing to do anything too complicated.   

What Does A 9mm Haircut Length Look Like? 

Here’s what a 9mm haircut “all over” looks like: 

It’s often shorter than people might initially think it would be. That’s why it’s important to look at photos like this before you reach for those blades and buzz it all down. 

It’s still short enough for the scalp to be quite visible, particularly if you’ve got thin or fine hair. 

Plus, it really isn’t long enough to style. This may be a problem for some, but ideal for others. As I mentioned, it makes hair grooming so much simpler because there really isn’t much you can do with it in the first place. 

It’s effortlessly neat and tidy without the need for brushes, combs, pomades, and so on. 

But there may be those men who might want to craft a style of some sort. Perhaps a short quiff or crop it forward into a slight fringe. 

As you can see from the photo, it really isn’t long enough for any of this. So be prepared for minimal styling options once you’ve trimmed it. 

If you’re simply looking for a versatile, sleek hairstyle without having to commit to something as short as a #0,#1, or #2, the #3 (9mm) haircut may be the one for you. 

Of course, as I mentioned earlier, one way of making the 9mm haircut a bit more interesting would be to add contrast between the top, back, and sides. 

Trim the sides short, fade them, craft an undercut or even a high-and-tight. You do still have options with buzz cuts; don’t forget this. 

If you aren’t sure, ask a barber to guide you in the right direction. 

I’ll finish off by talking about how the 9mm haircut is great for men with receding hairlines. 

It’s short enough to soften the transition from the forehead to the hair. In other words, receding hairlines just look less obvious. It may not be as good as the shorter buzz cut lengths for this, but it still works. 

A Great 9mm Hair Clipper To Try

The Wahl Color Pro gives you great value for money when you’re looking for a clipper to trim down to 9mm. 

Check it out on Amazon here. 

There are plenty of other clippers you could choose from. After all, you just need a clipper that comes with a #3 guard and there are many of those available. 

Some will be cheaper and many more will be more expensive. But don’t overcomplicate it. 

If all you’re looking to do is trim a simple, straightforward 9mm haircut all over, potentially with the sides/back trimmed a little shorter, the Color Pros will be fine. 

It’s one of the cheapest Wahl clippers out there. You get the great quality you’d expect from a Wahl clipper at a much better price. 

If you did want something a little more professional, the Wahl Magic Clips (Amazon Link) would be a good option. It does give you the benefit of a lever, which gives you additional control over length. It’s a favorite of barbers around the world. 

How To Easily Trim A 9mm Haircut All Over

Right – so you’ve got your tools sorted out. A good pair of clippers, a #3 clipper guard, and a bathroom mirror are really all you’ll need here. 

An additional handheld mirror would come in useful for the back, though. 

This routine will go through what you need to do to trim a 9mm haircut “all over”. In other words, an induction buzz cut. 

1. Fine-Tune Your Clipper 

You’ll want to do this before starting. 

Charge it, clean it, oil it. Simple. 

Charging it beforehand will make sure the motor runs strong enough to effortlessly clip through those long locks of yours. If it isn’t charged, you’ll realize it. It’ll tug, it’ll pull, and the trim won’t look as even. 

Clean it. The clipper most likely came with a small brush designed for sweeping away hair that’s clogged up around the blades. This hair will obstruct the blade and stop it from doing what it needs to do. 

Oiling the clipper blades beforehand is also important. It’ll reduce friction and ensure they’re working their best. 

2. Wash And Dry  

Rinse the hair before clipping, with or without shampoo. 

Buzzing it down is much easier when you’re dealing with clean and dry hair. Use a blow-dryer to really make sure the hair is dry before clipping. 

Clipping wet hair is inefficient as the hairs won’t catch as well. Plus, it just isn’t safe – electricity and water should never mix. 

Once your hair’s clean, it’s ready for the cut. 

3. Start Trimming Down To 9mm

It’s usually best to start with the top or sides before moving onto the back. You don’t have to, but the back will be harder so most men choose to leave it until last. 

The top and back are pretty straightforward though. 

Clip on the #3 clipper guard and start trimming. Trimming against the direction of hair growth (against the grain) will be faster and more effective. 

The hair on top generally grows forward, while the hair on the sides goes downward. So, you’ll want to trim the top backward, and the sides upward.  

Take your time and try to make sure you get as even a trim as possible. 

Now would be a good time to decide what you want to do with the sides and back. Although trimming fades is beyond the scope of this tutorial, it’s pretty easy to trim the sides and back down to a #2 (6mm) while leaving the top at a #3 (9mm). 

You can leave this decision until the end if you’d like to. In other words, trim everything down to 9mm first. 

If you find that the sides and back look a little too full or puffy, try clipping them down to 6mm while leaving the top at a slightly longer length. 

You’ll probably find that this gives the jawline more definition. 

4. Clip The Back Down To 9mm

The back is tough to trim yourself; that’s no secret. 

It’s hard to see and it’s hard to trim. There are dips and grooves that make running a clipper over it seem awkward and unnatural. 

If you’ve got someone that can do this part for you, that’s great. If not, don’t fret. It’s still perfectly possible with a bit of patience. 

If you’ve got a handheld mirror, use it. Turn around so your back is facing the bathroom mirror. Hold the handheld mirror in front of your face – you should be able to see the back of your head in its reflection thanks to the bathroom mirror behind you. 

Simple, right? 

Start clipping the back down to 9mm (or shorter if you wanted the contrast I mentioned in the earlier step). 

It’s easy to miss patches on the back of the head because it’s tougher to see. So, once you think you’re done, run your fingers over it to see if you can feel any uneven patches you’ve missed. 

These patches will feel rougher than the rest of your scalp. In fact, this is a good way of picking up on uneven patches all over your scalp, including the top and sides. 

Once you feel them, buzz them down. 

5. Sharpen Up The Neckline

The neckline is important when it comes to the 9mm haircut. What it refers to is the lowest point of the hair at the back of the head. 

It’s essentially where the hair meets the neck skin. 

When you’ve got 9mm’s worth of hair, an untidy neckline is pretty obvious. You can’t leave it long or “natural” because it’ll immediately come across as messy. 

With shorter buzz cut lengths like the buzz cut with no guard, this isn’t as big of a deal. The neckline isn’t very visible in the first place. 

But here, you’ll want to neaten it up. 

Again, this is a hard thing to do yourself, so if you’ve got someone that could do it for you it would be a lot easier. 

If you were going to DIY, you could try and freehand it by simply removing the guard and lining up the neckline using the clipper blade. It’s risky though. 

The best option would be to get yourself a neckline trimming template like this one on Amazon to avoid any mistakes. 

It’ll allow you to sharpen up (i.e straighten up) the neckline without the fear of shaky hands messing it up. 

6mm Vs 9mm Haircut

The 6mm haircut will reveal more of the scalp than the 9mm haircut and the stubble will also feel sharper to the touch. 

Here’s what it looks like: 

A mere small difference can actually seem like a whole lot once you’ve trimmed it down. Although 6mm’s worth of hair is still very visible, it still looks significantly closer to a bald head than 9mm does. 

Because shorter stubble is rougher and sharper to touch, 9mm hair does feel softer than 6mm hair. If this is something that’s important to you (or your partner), bear it in mind. 

Conclusion

It’s simple yet stylish. What’s great is that it’s pretty hard to go wrong with this style. 

It isn’t as daunting as trimming it all down to a #1, for instance. If you aren’t a fan of the results once you’ve trimmed down to 9mm, it probably won’t be long before you’re back at a length you find acceptable. 

So, if you aren’t sure, just give it a go. Most men that do find it hard to go back. 

Enjoy.

9mm Haircut: Guard Size Chart

A 9mm isn’t a standard guard size on all brands. Here’s how to get it right:

Pro tip: With Wahl or Andis clippers, the #3 guard gives you 10mm — very close to 9mm. For exact 9mm, use an adjustable clipper like a Philips Norelco or BaByliss with a precision dial.

How To Ask Your Barber For A 9mm Haircut

Here are the best ways to communicate a 9mm cut to your barber:

• Say: “Number 3 all over” or “Three-eighths of an inch all over”
• Be specific: “I want about 9-10mm on top and sides, all one length”
• For a fade: “Number 3 on top, faded to a 1 on the sides and back”
• Show a photo: A reference image removes all guesswork

The 9mm length sits right between a very short buzz and a medium one. It’s long enough to see slight hair texture but short enough to never need styling products.

Frequently Asked Questions

Axel Lander

Axel is the founder of ReadySleek and has spent over 5 years researching and testing men’s grooming products, skincare routines, and hair loss treatments. His work combines hands-on product testing with insights from dermatologists and trichologists to deliver evidence-based grooming advice.

He specializes in men’s skincare (including ingredient analysis of retinol, niacinamide, and SPF), hair loss science (minoxidil, finasteride, hair transplants), men’s fragrance (with 80+ colognes personally tested), and body grooming techniques.

When he’s not reviewing the latest grooming products, Axel focuses on making complex grooming topics accessible and actionable for everyday guys.