Acrylic Sheet Thickness and Type Guide: How to Choose the Right Perspex

Acrylic sheet and Perspex are the same material: Perspex is simply the best known brand name for acrylic, chemically known as PMMA. Glazing a shed window, building a shelf or specifying shopfit signage comes down to two decisions: thickness and type. This guide covers cast versus extruded acrylic, the right thickness for common jobs, finish options, and how to order it cut to size.

Cast vs Extruded Acrylic: Which Do You Need?

Two acrylic sheets can look identical off the roll, yet come from different production lines, cost around 20% apart, and behave very differently under a router or a laser. Cast acrylic is poured between two sheets of glass and cured slowly, giving superior optical clarity, a more consistent finish across large sheets, and clean flame-polishing, laser-cutting and thermoforming. Extruded acrylic is pushed continuously through a die, a faster, cheaper process holding a tighter thickness tolerance in thinner gauges, and suits routing, sawing and general glazing well.

Cast acrylic typically costs around 20% more than extruded acrylic of the same thickness. That premium buys better optical quality and better results under a laser or a flame polisher, so for display work, signage and fabrication it is worth paying.

 

For display pieces, laser-cut signage and anything that needs a flawless finish, shop Perspex cast acrylic sheet, cut to size. For general glazing and budget-conscious fabrication, browse our extruded acrylic sheet range instead.

Acrylic Sheet Thickness Guide

Order the wrong thickness and you find out at the worst moment: the shelf bows under a stack of books, or the shed window rattles in a gale. Across the trade, 2mm, 4mm, 6mm and 10mm Perspex sheet cover most everyday jobs, with 3mm, 5mm and 8mm filling the gaps.

2mm to 3mm suits the lightest jobs: picture-frame glazing, model-making, decorative splashbacks and photo blocks. 2mm is thin enough to score and snap by hand, and remains the default for frame replacements and small display pieces.

4mm to 5mm is the workhorse range for glazing. Shed windows, greenhouse panes, secondary glazing and light signage typically call for 4mm, stepping up to 5mm on larger or wind-exposed panes. This range also handles short-span, supported shelving and light guards.

6mm to 8mm starts to feel structural: longer shelving runs, table tops with edge support, heavier signage, partition screens and machine guards are usually specified here, since the extra thickness resists flex where a thinner sheet would bow.

10mm and above stops behaving like glazing and starts behaving like a building material: structural-look table tops with no sub-frame, plinths, display blocks, balustrade infill and pet barriers, and the sensible default wherever impact resistance genuinely matters.

What thickness do I need for:

• Shelf (short span, supported): 5mm to 6mm; move up to 8mm for longer runs without a supporting lip.

• Table top: 8mm on a sub-frame, 10mm where it needs to look solid on its own.

• Picture frame: 2mm, light and easy to cut to size for old frames.

• Shed window: 4mm for a like-for-like glass replacement; 5mm on larger panes.

• Secondary glazing: 4mm to 5mm; 3mm is workable on small panes but 4mm resists flex and rattle far better.

• Splashback: 3mm to 4mm, fixed flat to a wall so it carries no load of its own.

• Sneeze guard: 5mm extruded acrylic for most till and counter screens; 6mm to 8mm for taller, freestanding screens.

• Greenhouse pane: 4mm is the trade default, with 5mm worth considering on the largest panes.

• Cat flap or pet door: 6mm to 10mm, thick enough to resist a determined paw or nose without flexing in the frame.

A sheet's real-world strength is not just about thickness, it is about how far it spans unsupported and how it is fixed at the edges: the longer the span, the thicker the sheet, or the more support, you need to stop it flexing or sagging under load.

Myth: thicker acrylic is always the safer choice. Reality: oversizing the thickness on a small, well-supported panel just adds cost and weight. Matching thickness to span and support is the approach our fabrication team uses on every quote.

Clear, Coloured, Frosted, Mirrored and Non-Glare Acrylic: When to Choose Each Finish

A sign-maker rings most weeks asking for "the reflective one" without knowing there are several ways to get there. Clear, coloured, frosted, mirrored and non-glare acrylic sheet all start life as the same PMMA base; the finish is what turns a structural material into a design decision.

Clear is the default wherever visibility matters: glazing, display cases, guards and signage. Coloured or tinted works in opaque or translucent shades for retail fixtures and branded signage where the colour does the talking; browse the tinted acrylic collection for the full range. Frosted diffuses light evenly and hides fixings behind it, suiting privacy screens, bathroom panels and backlit signage. Mirrored gives a lightweight, shatter-resistant alternative to glass mirror, well suited to dance studios and changing rooms; see the mirror acrylic collection for stock sizes. Non-glare carries a textured surface that cuts reflections while keeping the image behind it sharp, the standard choice for picture framing and gallery display.

Standard Sheet Sizes and Cut to Size

Acrylic sheet does not arrive in the exact size your project needs. Suppliers across the trade typically stock acrylic plastic sheets in a handful of standard sizes and cut down from there.

Standard stock sheets typically run up to around 2440mm x 1220mm (8ft x 4ft) across the trade, with jumbo sheets up to roughly 3050mm x 2050mm from some suppliers for large single-piece work such as shopfronts or balustrade infill. Exact sizes and tolerances vary by supplier and batch, so treat these as a guide rather than a fixed spec.

Cut-to-size and shaped-cut services turn that stock sheet into the exact panel your project needs, from a rectangular shelf to a batch of identical brackets for a shopfit. Expect a cutting tolerance of around plus or minus 1mm on straight cuts from a properly set up panel saw or CNC router, tighter from laser cutting; ask for a confirmed tolerance on nested components or tight-fitting glazing.

Sheet acrylic ships with a protective film on both faces. Leave it on until the piece is fitted or displayed: it stops scratches during transport, storage and cutting, not just for show.

Once you know your thickness and finish, browse all acrylic sheet and order it cut to size.

Cutting, Drilling and Finishing Acrylic

Treat acrylic like wood on a cutting bench and you will crack more sheet than you save. It cuts cleanly with the right blade and speed, but the margin for error is smaller than most first-time users expect.

A fine-tooth blade in a jigsaw or bandsaw handles straight and curved cuts up to around 8mm to 10mm; a router with a single-flute cutter gives a cleaner edge on thicker sheet, and laser cutting delivers the sharpest, most repeatable edge of all. Keep the protective film on during cutting to reduce chipping. Drill with a reduced point angle: around 90 degrees for most hole sizes, versus roughly 118 degrees for a standard metal bit, stepping down toward 60 degrees only for larger-diameter holes, and back the bit off regularly so it does not overheat and grab.

Sand cut edges through progressively finer grits, then flame-polish or diamond-polish for a glass-clear finish. For the complete method, step by step, blade choice, scoring and snapping included, see our guide on how to cut Perspex.

Acrylic vs Glass vs Polycarbonate

Acrylic, glass or polycarbonate: which one actually suits your project?

Acrylic sheet is roughly half the weight of glass at the same thickness and offers markedly higher impact resistance, up to around ten times that of glass according to plastics industry technical data sheets, while staying clearer and more UV-stable than most other clear plastics. Glass still wins on scratch resistance and jobs needing an inert or heat-resistant surface. Polycarbonate steps in where impact resistance is the overriding priority, such as machine guarding, trading a little clarity for exceptional toughness. For the full head-to-head, read our Perspex vs Polycarbonate guide.

Caring for Acrylic: Cleaning and Longevity

Acrylic's biggest enemy is not scratching, it is the cleaning product reached for out of habit. Ammonia and solvent-based glass cleaners attack the surface, leaving fine cracks called crazing that no amount of polishing fully removes.

To clean acrylic sheet safely:

• Wipe with a soft, non-abrasive or microfibre cloth

• Use a dedicated plastic-safe cleaner, or warm water with a little mild soap

• Rinse and pat dry rather than dragging a cloth across a dry surface

Avoid: ammonia-based or solvent cleaners, paper towels, and abrasive scourers, which either attack the surface chemically or scratch it mechanically.

Acrylic sheet is inherently UV-stable and will not yellow under normal outdoor exposure, which is a large part of why it remains the material of choice for outdoor signage and glazing that needs to look good for years. A retailer's window display turned cloudy within a year of a shop-bought glass cleaner becoming the default on the till; switching to a plastic-safe cleaner has kept the replacement panel clear for three years and counting.

Frequently Asked Questions

Is Perspex the same as acrylic?

Yes. Perspex is a registered brand name for acrylic sheet (PMMA), not a separate material.

What thickness acrylic do I need for a shelf, table top or window?

5mm to 6mm for a shelf, 8mm to 10mm for a table top, and 4mm for a window replacement, stepping up to 5mm on larger panes.

Cast vs extruded acrylic: which is better?

Cast for display, signage and laser-cut work; it costs around 20% more but gives noticeably better optical quality. Extruded for general glazing and budget-conscious runs.

How thick should acrylic be for secondary glazing?

4mm is the standard for typical domestic window sizes; step up to 5mm on larger panes or draughtier older frames.

Can acrylic be cut to size?

Yes. It cuts cleanly by hand, on a router or CNC, or by laser, and arrives ready to fit with the protective film still in place.

Does acrylic yellow in sunlight?

No, not under normal conditions. Acrylic is one of the most UV-stable plastics available. It is polycarbonate, not acrylic, that typically needs a UV-stabilised coating to avoid discolouring.

Is acrylic stronger than glass?

Yes. Acrylic is around half the weight of glass at the same thickness with substantially higher impact resistance, though glass keeps the edge on scratch resistance.

Choosing the right acrylic sheet comes down to two decisions: cast or extruded, and the thickness that matches your span and load. Get those right and the finish is simply a matter of taste. We cut every order to size from stock Perspex cast and extruded acrylic sheet, ship it with the protective film still on, and are happy to talk through an unusual spec before you order.

Resources

• INEOS Acrylics, Perspex technical data sheets: cited for acrylic sheet's light transmission, weight relative to glass, and comparative impact resistance versus glass.

• Industry plastics technical data sheets (PMMA material property guidance): cited for general material property context on acrylic (PMMA).

Further reading:

• How to Cut Perspex

• Perspex vs Polycarbonate