Acrylic Thickness Chart: Standard 1.5mm–25mm

Metric or Inch: Which Thickness to Specify

US buyers usually specify inches; most global acrylic stock, including ours, is sold in millimeters. Asking for exactly 6.35mm (1/4 inch) when 6mm is stocked means custom-ordered sheet, a longer lead time, and a price premium for no structural difference. The chart anchors on stocked metric sizes and gives the nearest inch equivalent.

This is the chart we quote from. When the part is already drawn and you need it cut, polished and assembled, send the drawing through our custom acrylic fabrication page with the thickness you picked here.

Sheet thickness tolerances and optical data are published by PMMA sheet makers such as Plaskolite¹. Sheet tolerance and fabrication tolerance are different controls: our working tolerance standard covers cut parts, and the acrylic machining tolerance guide shows how to mark functional features on the approved drawing. The plexiglass vs acrylic terminology guide explains why “plexiglass thickness” and “acrylic thickness” charts are the same list.

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How to Choose Acrylic Thickness: Four Variables

Choose acrylic thickness by taking the thickest minimum set by four variables: load, unsupported span, edge exposure, and visual weight. Work through them in that order. If load says 3mm and span says 8mm, specify 8mm. Visual weight comes last because it is a design preference, not a structural requirement.

In my experience, most buyers approach thickness the wrong way. They pick a number from a reference photo, ask for “something sturdy,” or default to whatever thickness they saw on a competitor’s product. That works until it doesn’t — usually in month two of use, when the customer calls: a shelf that was supposed to hold six tablets is bowing like a hammock, or a box lid has cracked near a hinge point. The four-variable framework replaces guesswork with a repeatable decision. Load sets the minimum strength. Span amplifies deflection at any given thickness. Edge exposure determines whether you need a thickness that polishes cleanly. Visual weight is last because it’s a design preference, not a structural one.

Variable	What It Controls	Typical Outcome
Load	Minimum thickness for the weight carried	Sets the floor
Unsupported span	How thick to prevent sag between supports	Often pushes thicker than load alone
Edge exposure	Thickness that polishes cleanly (flame or diamond)	5mm+ for polished visible edges
Visual weight	Premium “solid” feel	Pushes to 8-10mm for awards, luxury display

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Acrylic Thickness by Product Type

Match your product category against the table below. These are the ranges Wetop uses in active production across 2,000+ custom projects: start inside the typical range, then adjust using the load and span table in the next section.

This matrix reflects what ships, not what’s theoretically possible. A display case can be built from 3mm — it’ll just crack on the first drop. Our typical ranges are conservative floors that hold up across 15-20 day production runs and survive international freight. Thicker than the range means you’re paying for structural margin you don’t need; thinner means you’re gambling on transit and handling.

Product Category	Typical Thickness	Notes
Small acrylic boxes	3mm walls, 5mm base	Lightweight gift and retail boxes; 3mm to 10mm walls compared in the acrylic box wall thickness guide
Display cases (countertop)	5-8mm walls, 8mm base	Add thicker base for stability
Display cases (floor standing)	8-10mm	10mm minimum for structural joints
Acrylic risers	3mm (small), 5-8mm (heavy)	Step up for weighted product
Countertop display stands	3-5mm	5mm default for retail handling
Acrylic shelves	5-10mm	Depends on span; see load table
Serving trays	5-8mm	5mm minimum for food contact
Award plaques	6-10mm	8mm reads as “premium”
Award blocks / trophies	15-50mm	Solid cast block, not sheet
Sign holders / card holders	2-4mm	Tabletop 3mm, wall-mount 4mm
Photo frames	3-5mm	3mm insert, 5mm magnetic backs
Shadow boxes	5mm face, 8mm frame	Depth drives frame thickness
Drawer organizers	3-5mm	5mm if loaded with heavy items

For a tray or case that touches food, also specify acrylic compliant with FDA 21 CFR 177.1010². The product pages for acrylic display cases, acrylic boxes, acrylic trays, and acrylic awards show these thicknesses in finished products. For trading card display cases, collectors typically specify 5mm walls and an 8–10mm base so the base carries graded slabs without rocking. Embedded acrylic logo blocks need at least 30mm total (two 15mm cast layers with the logo between), with 40-60mm for pieces where depth is part of the effect. An acrylic stamp block runs much thinner: 5–6mm for standard retail and 8–10mm for premium kits.

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Load and Span: How Thick Is Thick Enough?

For shelves, trays, and case tops, thickness only means something together with unsupported span. Doubling thickness makes a panel about 8 times stiffer. Doubling span increases sag 8 to 16 times, depending on whether the load sits in the middle or spreads evenly. Span is the variable I see underestimated most often on buyer drawings: 3mm holds 2 kg, but only over a short span.

The table below is conservative working guidance derived from the flexural modulus of cast PMMA (about 3,100 MPa)³. It assumes supports at both ends, evenly distributed load, clear cast acrylic, and room temperature. It is not engineering sign-off for safety-critical loads; for heavy retail, hospitality service, or anything overhead, add margin or a mid-span support.

Unsupported Span	Light Load (<2 kg)	Medium Load (2-5 kg)	Heavy Load (5-10 kg)
150mm / 6”	3mm	5mm	8mm
300mm / 12”	5mm	8mm	10mm
450mm / 18”	8mm	10mm	12mm + support
600mm / 24”	10mm	12mm + support	Not recommended — add mid-support
900mm / 36”	Mid-support required at all loads	—	—

Thin shelves over long spans sag visibly before they break. Boxes with undersized walls crack at corner joints under transit vibration. Trays flex under weight and stress glued corners. If a shelf sags under its design load, the thickness is wrong, and no edge polishing fixes that.

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Cast vs Extruded: Thickness Affects Material Choice

Above 10mm, cast acrylic is almost always the right choice: it machines cleaner and polishes brighter. Extruded sheet holds the tighter thickness tolerance, so on thick cast parts put the thickness tolerance on the drawing. Below 5mm, extruded sheet is usually acceptable and costs less. Between 5mm and 10mm, the choice depends on how the part is cut, finished and bonded.

Cast acrylic (sold as Perspex in the UK) is made by polymerizing liquid monomer between glass plates, which gives high molecular weight, good optical clarity, and good solvent resistance. Extruded acrylic is pushed through a die; it is dimensionally consistent and cheaper, but its lower molecular weight shows up as stress lines after edge polishing and a higher cracking risk when drilled. Thin sheets can also warp under UV lamp heat, which makes 5mm cast the safer minimum for UV printing on acrylic. Light transmission for both types is about 90-92% depending on thickness and color, measured with the ASTM D1003 method⁴. The cast vs extruded acrylic guide covers the full comparison.

Thickness	Best Choice	Why
1.5-3mm	Extruded	Cheaper, adequate clarity for signage
3-5mm	Either	Extruded for cost, cast for polished edges
5-10mm	Cast preferred	Better edge finish, less crazing
10mm+	Cast only	Machining quality, optical clarity
15mm+ (blocks)	Cast block	Cell-cast or solid casting, not sheet

Thickness and grade also matter at end of life; the guide on whether acrylic can be recycled separates clean factory offcuts from mixed post-consumer material.

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Fabrication and Cost Tradeoffs

Fabrication cost does not scale linearly with thickness. Raw sheet cost roughly doubles with thickness, but total per-piece cost at 10mm can be 2.5-3x the 3mm version of the same part — because every edge takes longer to cut, polish, bond, and inspect.

I walk buyers through three effects on every quote. First, laser cutting speed drops roughly in half as thickness doubles, and above 20mm we typically switch to CNC routing, which is slower again (the CNC vs laser cutting guide compares the two). Second, edge polishing scales with edge thickness: flame polishing for clean edges under 10mm, diamond polishing for the glass-clear finish buyers expect on awards and premium cases, as described in our edge finish standard. A diamond-polished edge on 12mm takes roughly three times the machine time of 5mm. Third, solvent bonding on thick pieces requires longer fixture and cure time, which extends production lead time from 15 days toward 20.

Process	3mm	5mm	10mm	20mm
Laser cut speed	Fast	Fast	Moderate	Switch to CNC
Edge polish time	Low	Low	High (diamond)	Very high
Solvent bond cure	Short	Short	Longer fixture time	Longer + slower cooling
Typical lead time impact	Baseline	Baseline	+2-3 days	+3-5 days
Typical cost multiplier vs 3mm	1x	1.3-1.5x	2.5-3x	4-5x

Multipliers are directional estimates from Wetop production records across display cases and award projects — not a published price list. For an exact quote on a specific thickness, send specs to inquiry@wetopacrylic.com and we respond within 24 hours.

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Common Acrylic Thickness Mistakes

Since 2014, I’ve catalogued these five thickness mistakes — they come from assumption, not bad intent, and most are easy to catch before production if you know what to look for. Together they account for the majority of thickness-related redesigns and returns we see across B2B orders.

1. Matching a competitor’s thickness without checking load. A competitor’s 3mm display stand might ship with lighter product inside. Spec for your actual load, not theirs.
2. Ignoring span on shelves and case tops. A 5mm shelf that works at 200mm will sag visibly at 500mm with the same weight.
3. Specifying imperial exactly when metric is stocked. Asking for 6.35mm (exactly 1/4”) when 6mm is stocked means custom sheet and a price premium for zero structural benefit. Use the nearest stocked metric size unless the design truly requires it.
4. Picking thick for “premium feel” on non-visible parts. A 10mm internal divider inside a 5mm case adds cost and weight for no visible return. Save thickness for edges and faces the buyer sees.
5. Under-specifying for transit. A box that is thick enough in use may still crack in international freight if corner joints are undersized. Build in 1-2mm margin on structural walls for anything shipping by sea.

For thickness decisions across a mixed product program, see the multi-category acrylic display rollout case study.

Footnotes

1. Plaskolite cast acrylic technical resources — US-based PMMA sheet manufacturer; their Downloads & Specs section publishes sheet tolerance and optical property data we cross-check against supplier quotes. ↩

2. FDA 21 CFR 177.1010 — Acrylic and modified acrylic plastics, semirigid and rigid (eCFR) — the US federal regulation defining which acrylic formulations are cleared for direct food contact. Required compliance for any serving tray, food-contact case, or display touching edible product. ↩

3. MatWeb acrylic (PMMA) material property database — aggregates published flexural modulus, tensile strength, and thermal data for cast PMMA from manufacturer datasheets. We use the ~3,100 MPa flexural modulus as the baseline for our load/span guidance tables. ↩

4. Cast acrylic sheet visible-light transmittance ~92% (ASTM D1003 luminous-transmittance method) — Röhm PLEXIGLAS technical page documenting the ~92% light transmittance of PMMA that underlies the 90–92% range cited for cast and extruded acrylic. ↩