Lash Extension Thickness: How to Choose, Chart & Calculator

Every lash stylist has two main goals: First, you want to give your clients the extensions they dream about. Second, you never want to compromise the health of their natural eyelashes.

The eyelash extension thickness you choose plays a big part in that, so getting it right is critical.

In this post, I make choosing the right extension diameter a fool-proof process, whether you’re creating classic or volume lashes.

Read on to learn how easy it can be when you have a handy lash thickness chart!

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What Does Lash Extension Thickness Mean?

Thickness has a significant impact on how much an extension will weigh, although the two terms (weight and thickness) are not the same thing. For example, a 0.07 mm extension will normally weigh around 0.04 mg, but length and material are also a factor.

What Are the Different Eyelash Extension Diameters?

Most suppliers carry the following lash extension diameters: 0.03, 0.05, 0.07, 0.10, 0.12, 0.15 mm, 0.18 mm, 0.20 mm up to 0.30 mm.

Having said that, I never ever use extensions thicker than 0.18 mm because from my experience they cannot be used safely. I’ll talk about this more a little later in the article.

Thin Lash Extensions

Extensions between 0.03 and 0.07 mm are considered very thin. Normally, they’re only used for volume-style extensions, where multiple extensions are attached to a single natural lash.

Medium Lash Extensions

Extensions between 0.10 and 0.12 mm are medium. They’re a very safe choice for classic sets where only one extension lash is attached to each natural lash. They are usually used on thinner natural lashes.

Thick Lash Extensions

Lashes between 0.15 mm and 0.18 mm are the thickest extensions you can use for classic sets. Only use them on clients with thick, strong natural lashes.

Overly-Thick Lash Extensions

Lashes between 0.20 to 0.30 mm should never be used. Regardless of how thick or strong your client’s natural lashes are, these are always too heavy.

How to Choose the Best Eyelash Extension Thickness

For example, if the client’s natural eyelashes have a thickness of 0.15 mm, you can choose an extension with a diameter ranging from 0.12 mm all the way up to 0.18 mm.

An extension that is too thin will not be visible, while an extension that is too thick will weigh down the natural eyelash.

Other factors such as the desired length and styling also come into play but they aren’t what you should first look at.

The following chart and calculator will make figuring it out a breeze. Consider printing them out so that they’re always handy!

Lash Extension Thickness Chart for Classic Lashes

Eyelash Extension Thickness chart	Thin Natural Lashes (0.10 mm to 0.12 mm)	Healthy Natural Lashes (0.12 mm to 0.15 mm)	Strong Natural Lashes (more than 0.15 mm)
0.03 mm Extension	No – not used for classic lashes.	No – not used for classic lashes.	No – not used for classic lashes.
0.05 mm Extension	No – not used for classic lashes.	No – not used for classic lashes.	No – not used for classic lashes.
0.07 mm Extension	Yes – Can be used if the client wants a slightly longer style*	No – not used for classic lashes.	No – not used for classic lashes.
0.10 mm Extension	Yes – Safe to use	Yes – Can be used if the client wants a slightly longer style*	No – too light.
0.12 mm Extension	Yes – Safe to use	Yes – Safe to use	Yes – Can be used if the client wants a slightly longer style*
0.15 mm Extension	Yes – Only for shorter extensions**	Yes – Safe to use	Yes – Safe to use
0.18 mm Extension	No – too heavy	Yes – Only for shorter extensions**	Yes – Safe to use

*Can be used if the client wants to extend their natural lashes by a little more than 2 mm. I generally don’t recommend going much longer than that.
**Can be used if the client wants to extend the natural lash by 1 mm or less.

Your first step, whether you’re creating a classic or volume set, is to determine what classic lash a natural lash can support. The chart above is applicable for classic lashes, where a single lash is attached to each natural lash.

You don’t need to break out a ruler to use this chart! You can conduct the measuring by simply placing an extension lash next to your client’s natural lash, and seeing how they compare.

Here’s an example of a client of mine with thin 0.10 mm natural eyelashes. Next, is an example of a client with strong 0.15 mm natural eyelashes.

Next, I’ll explain how you can determine the correct number of lashes to use in a volume fan based on the classic lash thickness.

Volume Lash Extension Weight Calculator

Volume Fan Weight Calculation	0.03 mm volume fan	0.05 mm volume fan	0.07 mm volume fan
0.10 mm classic lash	5 D	3 D	2 D
0.12 mm classic lash	7 D	4 D	3 D
0.15 mm classic lash	12 D	7 D	4 D
0.18 mm classic lash	18 D	10 D	5 D

Once you’ve found the perfect eyelash extension diameter for a classic set, you can use this calculator to identify what kind of volume lashes your client can handle safely.  

Please note that these are maximums! You can absolutely make the fans smaller, but don’t go any larger.

For example, if your client’s natural lash is 0.15 mm and could accommodate a 0.15 mm diameter extension, the maximum volume fans they can handle would be 12 D/0.03 mm, 7D/0.05 mm, and 4 D/0.07 mm.

But wait, how come 4 extensions of 0.07 mm diameter are the same weight as a single 0.15 mm extension? Because of negative space! I’ve covered this topic in my mega volume lash article here.

Online, some sources recommend larger fans, but in my experience, it damages the natural lash. Other sites don’t take into account the weight of the glue which leads to unsafe advice. The bigger the volume fan, the more glue is used.

What Happens When Your Lash Extensions Are Too Thick?

Thick lashes are heavy, uncomfortable, and can cause significant lash damage. They can even hurt by pulling on your natural lashes or poking your eyes. The stress on the natural lashes can lead to lash breakage and lash loss.

There’s also the risk that too much glue has been used, which can irritate the eyes and skin, or that a single extension lash has been attached to multiple natural lashes which can lead to even more significant lash damage.

That’s why getting it right the first time is so important. As a lash artist, the very lash thing you want to do is compromise your client’s natural lashes.

How to Fix Eyelash Extensions That Are Too Thick

The only way to fix overly-thick extensions is by having them professionally removed as soon as possible. Go back to your original lash technician and let her know about your discomfort, and have them professionally removed.

If you think your lash technician was negligent or inexperienced, consider going to a new salon with a better reputation. You could even show her this handy chart from this article 😉

I also have some tips for removing eyelash extensions at home safely.

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