Short answer: It depends on how it's cut. Laser-cut acrylic typically holds about ±0.005 in. (±0.13 mm) and CNC-routed parts about ±0.010 in. (±0.25 mm), while saw-cut blanks are commonly within about ±1/32 to ±1/16 in. Thickness is a separate tolerance set by the sheet maker: about ±5 to 10% for extruded and wider for cast, so 1/4 in. (6 mm) sheet can measure anywhere from about 0.21 to 0.26 in. Temperature matters too, since a 48 in. panel changes about 0.002 in. per °F.
Key facts
- Laser cutting: about ±0.005 in. on length and width, with a kerf of about 0.006 to 0.010 in.
- CNC routing: about ±0.010 in., including on 3/4 and 1 in. sheet.
- Table and panel saws: commonly about ±1/32 to ±1/16 in., depending on the saw and operator.
- Thickness: extruded about ±10% up to 3 mm and ±5% above; cast wider (ISO 7823-1 allows ±(0.4 mm + 10%)).
- Temperature: about 0.002 in. per °F on a 48 in. part, so measure at room temperature.
Tolerance by cutting method
| Method | Typical size tolerance | Edge | Notes |
|---|---|---|---|
| CO2 laser | about ±0.005 in. (±0.13 mm) | Glossy, flame-polished look | Any shape up to 1/2 in. thick; slight taper through thick sheet |
| CNC router | about ±0.010 in. (±0.25 mm) | Satin machined | Any thickness; square, stress-light edges for bonding |
| Table or panel saw | about ±1/32 to ±1/16 in. | Saw marks unless finished | Straight cuts only; squareness depends on setup |
| Score and snap | about ±1/16 in. or worse | Rough break | Straight cuts in thin sheet only; Plexiglas limits it to 0.236 in. and thinner |
These are typical figures for well-run equipment, not guarantees from every shop. If a dimension is critical, say so on your order and mark which side is the reference.
Why is the thickness tolerance bigger than the cut tolerance?
Because no cutting method changes the thickness. The sheet maker sets it. Extruded sheet is very uniform; Plaskolite's continuous cast OPTIX-L table, for example, allows 0.212 to 0.260 in. for nominal 0.236 in. (6 mm) sheet. Cast sheet is poured between glass plates and varies more across a sheet and from sheet to sheet. A "1/4 in." sheet is also usually 6 mm (0.236 in.), not 0.250 in. The full story, with each maker's tables, is in acrylic sheet actual thickness.
That's why slots, tabs, and edge channels should be designed from the measured sheet, not the label. For laser-cut slots we can cut to your measured thickness; see press-fit tolerances.
Does the laser cut exactly on the line?
The beam follows the line, and half the kerf comes off each side. On a laser that's about 0.003 to 0.005 in. per side, so outside dimensions come out slightly small and holes slightly large unless the path is offset. We compensate for kerf on outside profiles and holes so the finished part matches your drawing. The beam is also a narrow cone, so on 3/8 and 1/2 in. sheet the cut is a few thousandths narrower at one face than the other. See acrylic laser kerf.
How square is cut-to-size acrylic?
Laser and CNC parts are as square as the machine's axes, which on well-maintained equipment is well inside the size tolerance. Saw-cut blanks depend on the fence and miter setup; ACRYLITE's sawing guide calls for the fence to be parallel to the blade or opened just 1/64 to 1/32 in. at the back, and for blade runout under 0.002 in. To check any panel, measure both diagonals: if they match, it's square.
Does temperature change the size?
Yes, more than people expect. ACRYLITE gives a change of about 0.002 in. for each °F on a 48 in. panel. A part measured in a 55 °F garage and fitted in a 75 °F room has grown about 0.04 in. over 48 in. Humidity adds a little more. For frames and channels, leave clearance; ACRYLITE's glazing guide suggests cutting panels about 1/16 in. shorter than the opening for small lights, and more for big outdoor panels. The thermal expansion calculator does the math.
How do I order acrylic so it fits?
- Give the finished part size, not the opening size. Subtract your clearance first. See how to measure for acrylic cut to size.
- Say which dimensions are critical and which can vary.
- Pick the method for the job: laser for shapes and tight sizes up to 1/2 in.; routing for thick sheet or bonding edges.
- Design joints from measured thickness and leave room for its variation.
- Upload a drawing for anything that isn't a rectangle or circle, at 1:1 scale.
Our instant quote takes sizes to the thousandth and shows the price as you type, or upload a DXF or SVG.
Questions
Why is my pre-cut acrylic sheet smaller than the label?
Many stock blanks are cut from full sheets with a saw, and the blade kerf comes out of the nominal size, so a "12 × 12" blank can be 1/16 to 1/8 in. short. Custom-cut parts are cut to the size you order.
Can acrylic be cut tighter than ±0.005 in.?
Precision machining can hold tighter tolerances on small parts, but acrylic's thermal expansion means a few thousandths of an inch move with every few degrees. For most parts, ±0.005 in. is well beyond what the fit needs.
Can I order acrylic in an exact thickness?
Sheet comes in nominal thicknesses with the maker's tolerance. If you need a precise thickness, tell us; we can measure sheet and choose, or you can design around the measured value.