What Thickness Acrylic Do I Need?

It happens almost every day. Someone’s ready to order, they’ve got their dimensions sorted, they know the colour they want.. and then they hit the thickness dropdown and freeze. Is 3mm enough? Should they go 5mm to be safe? What about 8mm? They don’t want to order the wrong thing and either end up with something that flexes like a biscuit tin lid or spend twice as much as they needed to.

If that sounds familiar then this guide is for you. We’re going to work through the most common uses we see at Mitlee and give you a straight answer for each one. No hedging, no “it depends on many factors”,  just practical guidance so you can order with confidence.

Why Thickness Matters More Than You’d Think

Thickness affects almost everything about how a finished piece looks and behaves. A 2mm sheet is lightweight and easy to cut but will flex noticeably under its own weight across a larger span. While a 10mm sheet is rigid enough to use as a structural panel but takes more power to laser cut and requires sharper tooling to machine cleanly (and is considerably more expensive).

If you get it wrong it can be an expensive mistake A splashback that’s too thin will bow away from the wall. A machine guard that’s too light won’t meet safety expectations. A laser-engraved gift cut from sheet that’s too thick will take twice as long and may not engrave as cleanly. 

What's the Right Thickness for Your Project?

Picture Frames and Display Panels

For picture frames, photo blocks, and flat display panels, 2mm or 3mm is the standard. as it’s light enough to handle easily, gives a clean edge when cut, and sits flush without adding bulk. 3mm is the more popular choice as it it feels slightly more substantial and is a little easier to drill or edge-finish without risk of cracking.

Laser Cutting and Engraving

This is the most popular thickness for laser work is 3mm, and for good reason. It cuts quickly and cleanly with most CO2 laser machines, produces a sharp edge, and engraves with a crisp white frosted finish (provided you’re using cast acrylic, more on that below). 5mm works well too, particularly for pieces that need a bit more presence, but it requires more laser power and slower speeds.

If you’re cutting thicker than 5mm with a laser, bear in mind that most hobbyist and mid-range machines may struggle to get a clean cut in a single pass. Usually 3mm is the sweet spot for the vast majority of laser projects.

Retail Signage and Point-of-Sale Displays

Wall-mounted signs and hanging displays generally work well at 3mm to 5mm. For smaller A4 or A3 format signs, 3mm is fine. For larger panels or anything freestanding, A countertop display or a menu holder that needs to stand unsupported, go to 5mm. The extra thickness makes a real difference to how stable and professional the finished piece feels.

Machine Guards and Industrial Screens

This is where you start moving up the range. For machine guards, protective screens, and industrial barriers then5mm to 10mm is the working range, depending on the size of the panel and the level of impact resistance required. A small guard over a relatively low-risk area might be fine at 5mm but a larger panel spanning 600mm or more, or one that needs to withstand incidental contact, should be 8mm or 10mm. When in doubt in an industrial context, go thicker rather than lighter.

Aquarium Panels

Aquariums are one of the applications where people most often underestimate the thickness that they need. Water is heavy and hydrostatic pressure increases significantly with tank depth. As a rough guide 6mm is the minimum for a small tank (under 30cm high), 8mm for a medium tank and 10mm or above for anything larger or deeper.

If you’re building a custom aquarium, it’s worth doing a proper load calculation or consulting a fabrication specialist before you order as the cost of a panel is nothing compared to the cost of it failing. For most standard fish tank replacements or small custom builds 8mm is a sensible default.

Shelving and Load-Bearing Applications

If you’re using acrylic as a shelf that needs to carry any real weight, 8mm to 10mm is where you want to be, and the span matters as much as the thickness. A 10mm shelf spanning 400mm will hold up well. The same sheet spanning 800mm will show a noticeable bow under load. Keep spans short or increase thickness accordingly. 5mm shelving can work for very light decorative use, but don’t rely on it for anything heavier than a few small ornaments.

Splashbacks and Interior Design Features

For kitchen or bathroom splashbacks, 4mm to 6mm is the typical range. 3mm can work but may not sit as flat against the wall, particularly over larger areas where minor surface variations behind the sheet become more noticeable. 5mm or 6mm gives a more solid, premium feel and is easier to handle during installation. For coloured or mirrored acrylic used as a decorative wall feature, 4mm or 5mm strikes a good balance between visual weight and ease of fitting.

DIY Home Projects, Glazing, and Hobby Builds

This is probably the broadest category so the answer varies. For replacing a small glazed panel in a cabinet, a greenhouse pane, or a pet enclosure window, 3mm is usually right. It’s easy to cut with a scoring tool or fine-tooth saw, light enough to handle, and rigid enough over small spans. For larger panels anything over about 500mm in either dimension, move to 5mm to prevent flex. For hobby laser work and craft projects where you’re cutting shapes rather than structural pieces, 2mm or 3mm are both popular choices.

What Changes As You Go Thicker

It’s worth understanding what you’re actually trading off as thickness increases, because it’s not just about rigidity.

Rigidity increases significantly. A 6mm sheet is considerably stiffer than a 3mm sheet,  not just twice as stiff, because the relationship isn’t linear. This is what you’re usually buying with extra thickness.

Weight increases proportionally. A large 10mm panel is genuinely heavy and requires appropriate fixings and handling. Factor this in if you’re fitting something overhead or in a location where weight is a constraint.

Machinability changes too. Thicker sheet requires sharper tooling, slower feed rates on a CNC router, and more care when drilling to avoid cracking near edges. It’s not difficult, but it requires a bit more attention than cutting 3mm sheet.

Heat forming becomes harder with thicker material. Acrylic can be bent and shaped with a strip heater or oven, but thicker sheets need more heat, held for longer, and are less forgiving if you rush the process. 3mm bends easily; 8mm requires patience and the right equipment.

Cost increases with thickness, as you’d expect. There’s no point paying for 10mm sheet when 5mm does the job so use this guide to order what you actually need.

A Note on Ordering Cut to Size

One thing that catches people out is the assumption that they need to buy full sheets and cut them down themselves. You don’t — and with cast acrylic, cutting it badly at home is a real risk if you’re not set up for it.

At Mitlee, we cut every sheet to your exact dimensions before it leaves us. Our cut tolerance is ±1mm, using professional-grade equipment that produces a clean, accurate edge. You only pay for the material you actually need, there’s no offcut waste to deal with, and it arrives ready to use.

We dispatch within 1–3 working days via tracked courier, so for most projects you won’t be waiting long. If you’re working to a deadline, drop us an email and we’ll let you know what’s achievable.

Quick Reference: Thickness by Use 

Use the table below as a starting point. If your project sits between two thicknesses then go with the heavier option, you’ll rarely regret having a bit more rigidity.

Frequently Asked Questions

Is 3mm acrylic strong enough?

For most everyday uses, picture frames, small display panels, laser cutting, and short-span glazing then yes, 3mm is perfectly fine. It’s the most popular thickness we sell for good reason. Where it starts to fall short is over larger spans (500mm+) or in applications that require structural rigidity such as shelving or machine guards, step up to 5mm or above.

What thickness acrylic for a fish tank?

As a general rule, 6mm for small tanks (under 30cm high), 8mm for medium tanks, and 10mm or more for larger builds. Water pressure increases with depth, and undersized panels can flex or fail under load. If you’re unsure, go thicker rather than lighter — it’s not worth the risk.

Can I laser cut thick acrylic?

Yes, but there are practical limits depending on your machine. Most CO2 lasers handle 3mm to 5mm cast acrylic cleanly and efficiently. Above 5mm, you’ll need more laser power and slower cutting speeds to get a clean edge, and some hobbyist machines may struggle. 8mm and above is generally the territory of industrial or high-powered professional machines. For engraving rather than cutting, thickness matters less — you can engrave thicker sheet without issue.

What’s the thickest acrylic you can buy cut to size?

Our standard range runs from 2mm up to 10mm. If you need something outside that range, get in touch — we may be able to help depending on the colour and finish you need. For most projects, 10mm is more than sufficient, and anything beyond that starts to move into specialist fabrication territory.

Ready to Order?

If you know your thickness, head straight to our cast acrylic sheet range at mitleeplastics.co.uk and enter your dimensions. If you’re still not sure then please drop us a message at support@mitleeplastics.co.uk. We’re happy to help you pick the right spec before you order rather than after.

Written by the team at Mitlee Plastics — specialists in premium cast acrylic sheet, cut to size and delivered across the UK.