If you've ever ordered acrylic and had it arrive slightly too big for your bed, you'll know how annoying it is. You're either trimming it down by hand or leaving a strip of unusable material. Neither is ideal. Getting the size right before you order saves time, saves money, and means you can get straight into cutting.
This guide is aimed at hobbyists running smaller CNC routers. Machines like the WorkBee, Shapeoko, X-Carve, Genmitsu, and similar open-frame builds. We've matched up the most common working areas with the acrylic sheet sizes we stock, so you can order exactly what fits.
Why the Working Area Matters (Not the Frame Size)
This trips people up more than you'd think. The frame size of your machine is almost always larger than the actual working area. The gantry, limit switches, and carriage all eat into that space. A machine advertised as 1000 x 1000mm typically has a working area closer to 800 x 770mm.
So when you're ordering material, always go off your working area rather than your frame dimensions. If you're not sure what yours is, check the manufacturer's spec sheet or measure from homing position to the furthest point the spindle can actually reach.
There's also a practical reason to order slightly under your full working area. Workholding takes up space around the edges. Clamps, tabs, double-sided tape. Leaving 10-20mm of clearance on each side means you're not fighting for room when it matters.
Acrylic Sheet Sizes for Common Hobby CNC Machines
Here's a breakdown of the sizes that match up with the most popular hobby router working areas. We stock both 5mm and 6mm cast clear acrylic pre-cut to these dimensions. The right thickness depends on your project. 6mm is the more rigid option, better for structural panels, signs, and anything that needs to hold its shape unsupported. 5mm is slightly easier to cut on machines with less spindle torque and is a popular choice for engraving work and display pieces.
If you need a different size entirely, the cut-to-size tool lets you specify exact dimensions.
300 x 520mm (Small Bed Machines)
The entry point for most hobby CNC users. Machines in this class are compact, often desktop-sized, well-suited to smaller signage, engraving plates, display parts, and prototyping. The acrylic fits neatly on the bed with enough room around the edges to clamp down without interfering with the cut path.
Cast acrylic at this size is particularly forgiving for beginners. Smaller sheet means less flex, and it's easier to get flat on the spoilboard first time.
6mm Cast Clear Acrylic - 300mm x 520mm
550 x 520mm (Mid-Small Machines)
A step up from the compact class. At this size you've got enough room to run a decent-sized sign blank or do a small batch run of parts in a single setup. Popular with people who've outgrown the tiny machines but aren't ready to commit to a full metre square of working area.
One thing worth noting here. If you're running multiple passes or doing detailed work near the centre of the sheet, cast acrylic's tighter thickness tolerance (ours is +/-0.1mm vs the standard +/-0.2mm) makes a real difference. Consistent thickness means your Z depth stays accurate across the whole sheet.
5mm Cast Clear Acrylic - 550mm x 520mm
550 x 770mm (Mid-Size Machines)
This is where things start to get genuinely useful for small production work. The extra length opens up longer sign blanks. The kind of thing that would need repositioning on a smaller machine can often be done in one go here. 550 x 770mm is also a practical size for architectural panels, name boards, and anything that benefits from being taller than it is wide.
Works well for both router and laser use if you've got a hybrid machine setup.
5mm Cast Clear Acrylic - 550mm x 770mm
800 x 770mm (1000mm Frame Class)
This is the sweet spot for a lot of serious hobbyists and small workshop operators. Machines in the 1000 x 1000mm frame class are the most common step up from entry-level, and the 800 x 770mm working area gives you enough room to do proper work without the complexity of managing a larger bed.
At this size, material quality starts to matter more. Extruded acrylic can behave unpredictably on larger sheets. Slight variations in thickness cause Z depth issues, and the material can gum up under tooling rather than cutting cleanly. Cast acrylic machines more predictably, gives cleaner edges, and doesn't chip as badly on exit cuts.
If you're running a machine in this class and you've had frustrating results with cheaper acrylic, the material is often the culprit rather than the machine.
5mm Cast Clear Acrylic - 800mm x 770mm
800 x 1270mm (Long Bed Machines)
Long bed machines open up a class of work that smaller routers simply can't do in a single pass. Full-length sign blanks, furniture panel inserts, large format display pieces. Anything where the length is the constraint. The 800 x 1270mm sheet makes full use of that working length without leaving significant waste.
Worth mentioning for this size. The sheet will flex more than a smaller one if it isn't fully supported, especially across the longer axis. Make sure your spoilboard is flat and your workholding is solid before you start. Cast acrylic's rigidity helps here compared to thinner or extruded alternatives.
5mm Cast Clear Acrylic - 800mm x 1270mm
1200 x 1200mm (1500mm Frame Class)
The largest size in the hobby and semi-pro bracket. Machines running a 1500 x 1500mm frame are genuinely capable of commercial-scale output. At 1200 x 1200mm you're covering the vast majority of the working area on these machines and can tackle serious large-format work in a single operation.
At this scale, using cast acrylic isn't just a preference. It's the practical choice. Extruded sheet at this size is more likely to bow, varies more in thickness across the sheet, and cuts with a noticeably less clean edge on longer passes. Cast holds its flatness better and the surface quality is more consistent right to the edges. If you're putting a machine this size to work regularly, it's worth getting the material right.
6mm Cast Clear Acrylic - 1200mm x 1200mm
Also available slightly larger in 5mm: 5mm Cast Clear Acrylic - 1300mm x 1200mm
Why Cast Acrylic Specifically?
We only stock cast acrylic at Mitlee Plastics. That's a deliberate choice, not a gap in the range.
Extruded acrylic is cheaper to produce, and the saving gets passed down the chain. But for CNC routing, laser cutting, or any application where finish matters, cast is the better material. The manufacturing process results in better optical clarity, more consistent thickness, harder surface, and cleaner cuts under tooling. It also responds better to solvent bonding and engraves with sharper detail.
Our sheets carry a +/-0.1mm thickness tolerance, half the industry standard variance of +/-0.2mm. For CNC work that means your Z depth is accurate and consistent across the full sheet, not just in the centre where the bed tends to be flattest.
Need a Different Size?
If your machine has a non-standard working area, or you want a different thickness or colour, use the cut-to-size tool. You enter your exact dimensions and we cut and dispatch within 1-3 working days.
Not sure what you need? Drop us a message at support@mitleeplastics.co.uk and we'll point you in the right direction.
