Sheet goods are sold by a nominal thickness that is often not the thickness you get. A sheet of “3/4 inch” sheathing plywood is usually marked 23/32, and a “1/2 inch” sheet 15/32. This chart explains why, gives the real minimum and maximum thickness allowed for each size by the US product standards for plywood and OSB, and works out what a 4 x 8 sheet of each common panel weighs. Thicknesses come from the Department of Commerce standards PS 1 and PS 2; densities from the USDA Wood Handbook.
Plywood and OSB thickness chart
| Performance Category (label) | Allowed thickness, unsanded or OSB | Sanded plywood | Lb per 4×8, Douglas-fir plywood | Southern pine plywood | OSB (typical) |
|---|---|---|---|---|---|
| 1/4 | 0.219 to 0.281 in (5.6 to 7.1 mm) | 0.234 to 0.266 in | 24 | 26 | 30 |
| 5/16 | 0.281 to 0.344 in (7.1 to 8.7 mm) | 0.297 to 0.328 in | 30 | 32 | 37 |
| 11/32 | 0.313 to 0.375 in (8.0 to 9.5 mm) | 0.328 to 0.359 in | 33 | 36 | 41 |
| 3/8 | 0.344 to 0.406 in (8.7 to 10.3 mm) | 0.359 to 0.391 in | 36 | 39 | 45 |
| 7/16 | 0.406 to 0.469 in (10.3 to 11.9 mm) | 0.422 to 0.453 in | 42 | 45 | 52 |
| 15/32 | 0.438 to 0.500 in (11.1 to 12.7 mm) | 0.453 to 0.484 in | 45 | 48 | 56 |
| 1/2 | 0.469 to 0.531 in (11.9 to 13.5 mm) | 0.484 to 0.516 in | 48 | 52 | 60 |
| 9/16 | 0.531 to 0.594 in (13.5 to 15.1 mm) | 0.547 to 0.578 in | 54 | 58 | 67 |
| 19/32 | 0.563 to 0.625 in (14.3 to 15.9 mm) | 0.578 to 0.609 in | 57 | 61 | 71 |
| 5/8 | 0.594 to 0.656 in (15.1 to 16.7 mm) | 0.609 to 0.641 in | 60 | 65 | 75 |
| 23/32 | 0.688 to 0.750 in (17.5 to 19.0 mm) | 0.703 to 0.734 in | 69 | 74 | 86 |
| 3/4 | 0.719 to 0.781 in (18.3 to 19.8 mm) | 0.734 to 0.766 in | 72 | 78 | 90 |
| 7/8 | 0.831 to 0.919 in (21.1 to 23.3 mm) | 0.849 to 0.901 in | 84 | 91 | 105 |
| 1 | 0.950 to 1.050 in (24.1 to 26.7 mm) | 0.970 to 1.030 in | 96 | 103 | 120 |
| 1-1/8 | 1.069 to 1.181 in (27.2 to 30.0 mm) | 1.091 to 1.159 in | 108 | 116 | 135 |
| 1-1/4 | 1.188 to 1.313 in (30.2 to 33.4 mm) | 1.213 to 1.288 in | 120 | 129 | 150 |
Why 3/4 plywood is 23/32
Structural panels are labelled with a Performance Category, which PS 2 defines as a designation tied to a thickness range and to the nominal thicknesses the building codes refer to. The category on the stamp is the thickness the panel was made to, and PS 2 allows plus or minus 1/32 in on it for panels up to 13/16 (and plus or minus 5% above that). So a 23/32 CAT panel may measure anywhere from 0.688 to 0.750 in, and a 3/4 CAT panel 0.719 to 0.781 in. Both are sold as “3/4 plywood”. The code treats them as the same nominal thickness, but in cabinetry and joinery the difference matters: a dado cut with a 3/4 in bit will be loose on a 23/32 panel.
Sanded plywood (the A and B face grades used for cabinets and furniture) has a tighter tolerance in PS 1, plus or minus 1/64 in up to 3/4, because the faces are sanded to size. Hardwood plywood with oak, birch or maple faces is made to a different standard (ANSI/HPVA HP-1) and is commonly a little under its nominal size too, so measure the sheets you actually have before setting up a router bit or a dado stack.
Sheet size, squareness and moisture
- Length and width. PS 1 allows plus zero, minus 1/16 in on the stated size, so a “4 x 8” plywood sheet is at most 48 x 96 in and may be up to 1/16 in smaller. Panels marked “sized for spacing” are made up to 1/8 in under so that a 1/8 in gap can be left between sheets. PS 2 allows plus or minus 1/16 in.
- Squareness. Both standards require panels to be square within 1/64 in per foot of the longest edge, measured on the diagonals: for a 4 x 8 sheet the diagonals may differ by about 1/8 in. Do not use a factory edge as a reference for fine work without checking it.
- Moisture. Plywood may leave the mill at up to 18% moisture content under PS 1, and PS 2 panels must be under 16%. PS 1 measures panel size at 9%. Panels swell as they take on moisture, which is why sheathing is gapped and why sheets should be stored flat and dry and allowed to settle in the room before building furniture.
Weight and density of sheet materials
| Material | Specific gravity (Handbook) | Lb per ft³ (typical) | Lb per 4×8 sheet, 3/4 in (range) | Lb per sq ft, 3/4 in | Source |
|---|---|---|---|---|---|
| Plywood, Douglas-fir | 0.53 | 36.1 | 72 | 2.25 | Table 12-2 |
| Plywood, southern pine | 0.57 | 38.8 | 78 | 2.42 | Table 12-2 |
| Plywood, western redcedar or redwood | 0.41 | 27.9 | 56 | 1.74 | Table 12-2 |
| Plywood, lauan | 0.44 | 29.9 | 60 | 1.87 | Table 12-2 |
| OSB | 0.51 to 0.80 | 44.9 | 90 (69 to 109) | 2.81 | Table 12-3, 22 mills, median 0.66 |
| Particleboard | 0.60 to 0.77 | 48.3 | 97 (82 to 105) | 3.02 | Table 12-4, 9 mills, median 0.71 |
| MDF | 0.71 to 0.95 g/cm³ | 49.6 | 99 (89 to 119) | 3.10 | Table 12-6, 8 mills, median 0.80 (density, g/cm³) |
| Hardboard | 0.90 to 1.02 | 64.3 | 129 (122 to 139) | 4.02 | Table 12-5, 10 products, median 0.95 |
Worked examples
Can one person carry it? A 23/32 sheet of Douglas-fir plywood works out at about 69 lb, a 3/4 in sheet of MDF at about 99 lb. The MDF is 44% heavier for the same size, so plan for a helper, a panel cart or having the yard make the first cuts.
Loading a roof. 7/16 OSB sheathing at the median Handbook density is about 52 lb per sheet, or 1.64 lb per square foot. A roof of 40 sheets is about 1.0 tons of OSB before shingles; when sheets are lifted onto a roof, ask for them to be spread out rather than stacked in one spot.
Weight from the label. If you know the actual thickness and the product, multiply: weight per sheet = density (lb/ft³) x 32 sq ft x thickness (in) / 12. For 5/8 MDF at 49.6 lb/ft³: 49.6 x 32 x 0.625 / 12 = 83 lb.
Plywood or OSB: what the Handbook tests show
The Handbook’s Table 12-2 gives bending stiffness (MOE) of 1.01 to 1.24 million psi and bending strength (MOR) of 4,890 to 6,180 psi for plywood sheathing of six species. Its OSB data (Table 12-3) show the effect of strand orientation: along the strength axis, OSB stiffness ranges from 0.64 to 1.15 million psi; across it, only 0.20 to 0.46 million psi. That is why OSB and plywood sheathing must be installed with the long direction (the strength axis, marked on the panel) across the joists or rafters.
For structural use the comparison that counts is the span rating, not the species. PS 2 rates every structural panel for an application and a support spacing: “32/16” means the panel can be used as roof sheathing over supports 32 in apart and as subflooring over supports 16 in apart. Plywood and OSB with the same span rating and Performance Category are accepted for the same uses. PS 2 also notes that the US building codes require at least a 3/8 Performance Category for wall sheathing. For everything structural, follow the stamp on the panel and your local code.
Common mistakes
- Cutting dadoes and rabbets to nominal size. Measure the panel, or use an undersized plywood bit made for 23/32 stock.
- Mixing sheets from different bundles in one glue-up or cabinet. Two “3/4” panels can differ by more than 1/32 in.
- Leaving no gap between sheathing panels. Unless the panels are “sized for spacing”, leave about 1/8 in at ends and edges so swelling does not buckle the roof or floor.
- Using interior MDF or particleboard where it can get wet. Both swell permanently at edges exposed to water; use exterior-rated panels or seal every edge.
Frequently asked questions
How thick is 3/4 plywood really?
Structural “3/4” plywood is usually a 23/32 Performance Category panel, which PS 2 allows from 0.688 to 0.750 in. A 3/4 CAT panel may be 0.719 to 0.781 in. Sanded 3/4 plywood is held to 0.734 to 0.766 in by PS 1.
How much does a sheet of 3/4 plywood weigh?
About 69 lb for a 23/32 Douglas-fir sheet and 74 lb for southern pine, at 9% moisture content (our calculation from Wood Handbook densities). Hardwood-faced plywood and wet sheets weigh more.
How much does a 4×8 sheet of OSB weigh?
For 7/16 OSB, about 52 lb at the median Handbook density, with a range of about 40 to 64 lb across the 22 mills in Table 12-3. 23/32 OSB is about 86 lb.
How heavy is a sheet of MDF?
A 3/4 in 4×8 sheet of MDF is about 99 lb at the median density in the Handbook (0.80 g/cm³), and from 89 to 119 lb across the 8 products it lists.
What does 15/32 mean on plywood?
It is the Performance Category: the panel is made to 15/32 in (about 0.47 in) and is accepted wherever the code calls for nominal 1/2 in sheathing. PS 2 allows 0.438 to 0.500 in for this category.
Sources
- US Department of Commerce, Voluntary Product Standard PS 2-18, Performance Standard for Wood Structural Panels (NIST, 2018): Table 1 panel thickness; sections on size and thickness tolerance, squareness, moisture content and span ratings.
- US Department of Commerce, Voluntary Product Standard PS 1-22, Structural Plywood (NIST, 2023): Table 10 plywood thickness (unsanded and sanded); size tolerance, measurement at 9% moisture content and moisture at shipment.
- USDA Forest Products Laboratory, Wood Handbook FPL-GTR-190 (2010), chapter 12, Tables 12-2 (plywood), 12-3 (OSB), 12-4 (particleboard), 12-5 (hardboard) and 12-6 (MDF).
Last reviewed: 24 October 2026. Thickness limits are transcribed from the standards; weights are our calculation, shown in each table caption. Related: plywood grades explained (A, B, C, D, CDX), plywood cut calculator, cut list optimizer, the lumber dimensions chart and the wood species database. Spotted an error? Please let us know.