How Strong Is Acrylic? Strength, Impact, and Design Tips

Short answer: Acrylic sheet has a tensile strength of about 10,000 to 11,000 psi (69 to 76 MPa, ASTM D638), a flexural strength around 16,000 psi, and a flexural modulus of about 450,000 to 480,000 psi; Röhm and Acrylite rate it about 11 times as impact-resistant as ordinary glass. But it's brittle (about 4 to 5% elongation), notch-sensitive, and creeps under constant load, so makers limit continuous stress to about 1,500 psi for cast and 750 psi for extruded sheet.

How strong is acrylic, by the numbers?

Typical room-temperature values from sheet makers' data sheets. They're typical values, not specifications, and vary with grade and thickness.

Property (test)	Acrylite cast	Acrylite extruded (FF)	Plexiglas G (cast)	Optix-L
Tensile strength (ASTM D638)	10,000 psi	10,000 psi	10,500 psi	11,000 psi
Tensile modulus	400,000 psi	400,000 psi	450,000 psi	465,000 psi
Flexural strength (ASTM D790)	16,500 psi	17,000 psi	16,000 psi	14,700 psi
Flexural modulus	475,000 psi	480,000 psi	450,000 psi	461,000 psi
Compressive strength (ASTM D695)	18,000 psi	17,000 psi	n/a	n/a
Elongation at break	4.2%	4.5%	4.9%	n/a
Notched Izod impact (ASTM D256)	0.4 ft-lb/in	0.4 ft-lb/in	0.3 ft-lb/in	0.32 ft-lb/in
Rockwell hardness (ASTM D785)	M-94	M-93	M-100	M-100

Density is 1.19 g/cm³ for all of them, about half the weight of glass. Acrylite also lists a shear strength of 9,000 psi for cast sheet. Steel, for comparison, is roughly 60 times stiffer, so acrylic usually fails by sagging or cracking long before it "breaks" in the textbook sense.

Is acrylic stronger than glass?

For impact, yes. Röhm describes PLEXIGLAS as 11 times more break-resistant than glass, and Acrylite says its cast block has eleven times the impact strength of glass. (You'll see "17 times" quoted around the web; we couldn't find a maker's data sheet that says so.) When acrylic does break, Acrylite notes it breaks into comparatively large pieces rather than small slivers, and cast sheet from 0.080 to 0.500 in. meets the ANSI Z97.1 safety glazing standard. Glass is stiffer and far more scratch-resistant. Acrylic vs glass.

Is acrylic stronger than polycarbonate?

Acrylic is a bit stiffer and has similar tensile strength, but polycarbonate is far tougher in impact: it dents and bends where acrylic cracks. For machine guards, anything that might be hit or kicked, and security glazing, choose polycarbonate. For clarity, scratch resistance, and polished edges, acrylic. Acrylic vs polycarbonate.

Why does acrylic crack?

Acrylic stretches only about 4 to 5% before it breaks, so it doesn't redistribute stress the way metals do. The Madison Group, a plastics failure-analysis firm, notes that a sharp scratch just 0.01 in. deep can cut acrylic's tensile strength by about half. Anything that concentrates stress is where a crack starts:

Sharp inside corners. A square inside corner in a cutout can multiply local stress several times. Round it: even a 1/16 to 1/8 in. radius helps a lot.
Holes. A round hole roughly triples the stress at its edge under tension. Keep holes at least 1.5 hole diameters from edges (Röhm) and drill cleanly.
Rough edges and chips. Saw chatter and chips act like tiny notches. Smooth edges are stronger edges.
Overtightened screws. A clamped screw head plus thermal expansion is a classic cracking point.
Built-in stress plus chemicals. Laser cutting, flame polishing, and bending leave stress that can craze when solvents touch it. See why laser-cut acrylic cracks later.

How much continuous load can acrylic take?

Much less than its short-term strength. Under steady load acrylic creeps (keeps deflecting) and, above a certain stress, crazes. Sheet makers set long-term limits well below the 10,000 psi test value:

Acrylite cast: continuously imposed design loads should not exceed 1,500 psi (10.4 MPa).
Acrylite extruded (FF): 750 psi (5.2 MPa) continuous at 73 °F, with short-term loads up to 1,500 psi.
Röhm PLEXIGLAS GS/XT: maximum safety stress of 5 to 10 MPa (about 725 to 1,450 psi) up to 104 °F (40 °C).
Over decades: the Madison Group cites creep-rupture design stresses of 1,500 psi for a 10-year life and 650 psi for 20 years.

Strength also falls with heat: Röhm lists cast PLEXIGLAS at about 11,600 psi (80 MPa) at 73 °F but about 5,800 psi (40 MPa) at 158 °F (70 °C). That's why shelves and tanks are designed so conservatively. See how much weight an acrylic shelf can hold and the shelf sag calculator.

How do you design stronger acrylic parts?

Go thicker. Stiffness rises with the cube of thickness: doubling thickness makes a panel about 8 times stiffer.
Round every inside corner and avoid narrow necks and slots that end in a sharp point.
Keep holes away from edges and drill them slightly oversize for screws.
Add a bend or a rib. A bent lip or a bonded stiffening strip makes a thin panel much stiffer.
Support it evenly. Spread loads with washers, channels, or full-length supports rather than point loads. Acrylite says large sheets belong in frames, not bolted.
Choose cast for sustained loads, and keep solvents away from loaded or stressed areas.

Not sure what thickness you need? Read what thickness acrylic do I need, or describe your project and we'll suggest one. Cut parts with rounded corners and clean holes are in the instant quote.

Questions

Can you stand on acrylic?

Thick acrylic over a short span can carry a person, and acrylic floor panels exist, but they're engineered by specialists with thick sheet and full support. Don't stand on ordinary acrylic panels or improvised steps.

Will acrylic break if I drop it?

Thin acrylic usually survives drops that would break glass, but a corner hitting concrete can chip or crack it. Thicker sheet is more resistant, and polycarbonate almost never breaks from drops.

Is acrylic weaker in the cold?

Its tensile strength actually rises in the cold (Röhm lists about 16,000 psi at -40 °F), and Acrylite rates cast sheet for use down to -40 °F, but it gets more brittle, so impacts crack it more easily in freezing weather. See acrylic in cold weather.

Is a glued acrylic joint as strong as the sheet?

Not quite. Röhm puts its best two-part cement joints at up to 75% of the sheet's strength, and the Madison Group cites 70 to 90% for well-made bonded joints. Bubbles and gaps lower that. See how to glue acrylic.

How strong is acrylic?