Short answer: For most projects: 1/8 in. (3 mm) for picture frames, jewelry, cake toppers, and small signs; 1/4 in. (6 mm) for wall signs, sneeze guards, and boxes over about 12 in.; and 3/8 to 3/4 in. for shelves, depending on span and load. Stiffness grows with the cube of thickness, so doubling thickness makes a panel about eight times stiffer; the bigger and less supported the panel, the thicker it needs to be.
Key facts
- Most common thicknesses: 1/8 in. (3 mm) and 1/4 in. (6 mm).
- Stiffness: a flat panel's stiffness grows with thickness cubed. 1/4 in. is about 8 times as stiff as 1/8 in.; 1/2 in. about 8 times as stiff as 1/4 in.
- Weight: 1/8 in. ≈ 0.73 lb/ft², 1/4 in. ≈ 1.46 lb/ft², 1/2 in. ≈ 2.9 lb/ft² (density 1.19 g/cm³).
- Long-term load: acrylic creeps. Acrylite advises keeping continuous stress under 1,500 psi for cast sheet (750 psi for extruded glazing), far below its 10,000 psi tensile strength.
- Labels are nominal: real sheet usually measures a little different.
Quick rules of thumb
- Supported on its whole back (table covers, frames, signs mounted flat): thickness is about looks and handling, so thin is fine.
- Supported at the edges or a few points (shelves, standoff signs, windows): stiffness matters, and it rises with the cube of thickness.
- Standing on its own edge (sneeze guards, dividers, stands): too thin and it wobbles and bows.
- Holding water or weight for years (tanks, shelves): acrylic slowly deforms under constant load (manufacturers call it cold flow), so size it generously.
Thickness chart by project
| Project | Recommended thickness | Notes |
|---|---|---|
| Jewelry and earrings | 1/8 in. (3 mm) | 1/16 in. for very light pieces; thin parts with fine detail break more easily |
| Cake toppers | 1/8 in. | Thinner toppers snap at the stake; keep script lettering connected and at least about 1/8 in. wide |
| Keychains, ornaments, tags | 1/8 in. | 3/16 in. for a more solid feel |
| Place cards, table numbers | 1/8 in. | 3/16 in. if they stand without a base |
| Coasters | 1/8 to 1/4 in. | 1/4 in. feels substantial |
| Picture frame fronts | 1/8 in. up to about 24 × 36 in. | Framing grades are made 0.060 to 0.118 in.; 3/16 in. for larger frames so the sheet doesn't bow |
| Small signs, door and name plates | 1/8 in. | Up to about 12 in. wide |
| Wall signs on standoffs | 1/4 in. | 3/16 in. for small signs; 3/8 in. for signs over about 36 in. or for a heavy edge |
| Edge-lit LED signs | 1/4 in. | 3/8 in. gives a brighter, wider glowing edge |
| Wedding and event signs | 1/4 in. | 3/16 in. for tabletop sizes |
| Sneeze guards and counter shields | 1/4 in. | 3/16 in. for desk shields up to about 24 × 24 in.; 3/8 in. for very large panels |
| Desk dividers | 3/16 to 1/4 in. | Depends on height and how they mount |
| Shelves, up to 12 in. span, light items | 1/4 in. | Spans are between supports |
| Shelves, 12 to 24 in. span | 3/8 to 1/2 in. | 1/2 in. for books or anything heavy |
| Shelves, 24 to 36 in. span | 1/2 to 3/4 in. | Use the shelf sag calculator |
| Shelves, 36 to 48 in. span | 3/4 to 1 in. | Or add a middle support |
| Display cases under 12 in. | 1/8 in. | Bonded or slotted |
| Display cases 12 to 24 in. | 3/16 to 1/4 in. | 1/4 in. for a crisp, solid look |
| Display cases over 24 in. | 1/4 to 3/8 in. | 3/8 to 1/2 in. for large floor cases |
| Table top covers on a solid table | 1/8 in. | 1/4 in. for heavy use or a more glass-like look |
| Table tops spanning an open frame | 1/2 in. or more | Depends on span; ask us |
| Window inserts and storm panels | 1/8 in. | Supported in a frame on all four sides |
| Replacement windows (sheds, coops, barns) | 1/8 in. up to about 24 in.; 1/4 in. larger | Allow for expansion in the frame |
| Machine guards | 1/4 in. | Consider polycarbonate where parts can fly |
| Electronics enclosures, robot frames | 1/8 to 1/4 in. | 1/4 in. or thicker if you need tapped holes |
| Router and saw templates | 1/4 to 1/2 in. | Thick enough for the bearing on your bit |
| Quilting templates | 1/8 in. | Standard for rotary cutting |
| Phone and tablet stands | 1/4 in. | Bent or slotted |
| Dry-erase boards | 1/4 in. | Stiff enough to write on when mounted on standoffs |
| Aquariums and tanks | Depends on water depth | Use the aquarium calculator and an experienced builder |
These are our starting points for typical sizes, not engineering numbers. Unusual loads, spans, or sizes deserve a closer look.
How thick should an acrylic shelf be?
Shelves are where thickness matters most. A shelf supported at both ends sags in the middle, and the sag grows very quickly with span: for the same load per inch of shelf, doubling the span makes the sag about 16 times larger; for the same total load, about 8 times. Acrylite warns that large flat sheet can deform permanently under continuous load, so a shelf that sags a little on day one will sag more after a year. Aim for very little visible sag. Run your own numbers in the acrylic shelf sag calculator, and read how much weight an acrylic shelf can hold.
How thick should a sign be?
For a sign mounted on standoffs, 1/4 in. is the default: it looks substantial, stays flat between the mounting points, and holds the standoff holes well. Signs mounted flat with tape can be 1/8 in. Larger signs, over about 36 in. on a side, look and hang better at 3/8 in. Outdoor signs face wind and temperature swings, so step up a size and leave room for thermal expansion: Plaskolite's rule of thumb is to allow about 1/16 in. per linear foot. Large outdoor sign faces are sized to the local design wind load, so check your local code.
How thick should aquarium acrylic be?
That depends mostly on water depth, then on panel length and how the tank is built. Small, shallow tanks can use 1/4 in.; most real aquariums use 1/2 in. and up. Plan with the aquarium thickness calculator and read acrylic aquarium thickness. A tank failure means a lot of water on the floor, so treat any calculation as planning only.
Thicker isn't always better
- Weight. 1/4 in. acrylic weighs about 1.46 lb per square foot; 1/2 in. about 2.9 lb. A full 4 × 8 ft sheet of 1/2 in. is over 90 lb.
- Detail. Fine laser-cut details, small holes, and thin bridges are easier in thinner sheet.
- Bending. We line-bend up to 1/4 in.
- Cost. Price rises with thickness, so don't go thicker than the job needs.
Once you know your size and thickness, see your price instantly in the instant quote. If you're still unsure, describe the project on make it in acrylic and we'll suggest a thickness.
Questions
What is the most common acrylic thickness?
1/8 in. (3 mm) and 1/4 in. (6 mm) cover most projects. 1/8 in. is the standard for frames, crafts, and small parts; 1/4 in. is the standard for signs, guards, and anything that needs to feel solid.
Should acrylic be thicker than the glass it replaces?
Usually the same thickness or one size up. Acrylite notes acrylic is not as rigid as glass, so a large panel with only edge support flexes more, but it resists breaking several times better, so it doesn't need extra thickness for strength.
How thick does acrylic need to be for tapped screw holes?
At least 1/4 in. Thinner sheet doesn't have enough material for the threads to hold; use through-bolts or nuts instead.
How far can acrylic bend without heat?
Not far. Plaskolite gives a minimum cold-bend radius of 200 times the sheet thickness, so 1/8 in. sheet needs a curve of about 25 in. radius or more. Tighter bends need heat; see how to bend acrylic.