Plywood Thickness and Grades Chart
Plywood comes in a range of thicknesses, grades, and veneer species that can be confusing even for experienced builders. The charts below cover the three things most people need to know: actual thickness vs nominal thickness (they're not the same), what the grade letters mean (A, B, C, D), and which thickness and grade to use for which application.
Plywood Thickness — Nominal vs Actual
Like dimensional lumber, plywood's nominal thickness doesn't match its actual measured thickness. A sheet sold as "3/4 inch plywood" typically measures 23/32" (0.719"). This matters when planning flush transitions, sizing dados, or calculating weight.
| Nominal | Actual | Decimal |
|---|---|---|
| 1/4" | 1/4" | 0.250" |
| 3/8" | 11/32" | 0.344" |
| 1/2" | 15/32" | 0.469" |
| 5/8" | 19/32" | 0.594" |
| 3/4" | 23/32" | 0.719" |
| 1" | 31/32" | 0.969" |
| 1-1/8" | 1-3/32" | 1.094" |
Why the Discrepancy?
Plywood thickness standards allow for manufacturing tolerance and the sanding process. The APA Engineered Wood Association defines actual thickness as nominal minus approximately 1/32" for most softwood plywood panels. The exception is 1/4" plywood, which is typically sold at a full 1/4" actual.
Baltic birch and hardwood plywood are the exceptions to the nominal/actual discrepancy. Baltic birch is sold in metric thicknesses (3mm, 6mm, 9mm, 12mm, 15mm, 18mm) and the actual thickness matches the stated thickness. Domestic hardwood plywood may vary by manufacturer.
Plywood Grade Chart
Plywood grades describe the quality of the face and back veneers. A panel has two designations — one for the face (better side) and one for the back. The grading system uses letters A through D for softwood structural plywood.
| Grade | Description |
|---|---|
| A | Smooth, paintable. Minor patches allowed, no knots. |
| B | Solid surface. Small knots, patches, minor splits allowed. |
| C-Plugged | Improved C grade. Small knotholes plugged, limited splits. |
| C | Knotholes up to 1.5", limited splits. Minimum for exterior exposure. |
| D | Knotholes up to 2.5", larger splits allowed. Interior use only. |
Common Grade Combinations
| Stamp | Face / Back | Typical Use |
|---|---|---|
| A-A | Smooth both sides | Cabinet doors, furniture, visible both sides |
| A-B | Smooth face, solid back | Cabinets, shelving (one side visible) |
| A-C | Smooth face, utility back | Exterior finish applications, siding substrate |
| B-C | Solid face, utility back | Utility shelving, shop projects, concrete forming |
| C-D (CDX) | Utility face, interior back | Roof sheathing, wall sheathing, subfloor |
| C-C | Utility both sides, exterior glue | Exterior structural, permanent outdoor exposure |
The "X" in CDX
CDX is the most commonly purchased plywood grade, and the "X" is the most commonly misunderstood letter in construction. The X stands for Exposure 1glue — meaning the adhesive can handle temporary moisture exposure during construction, but the panel is NOT rated for permanent outdoor exposure. CDX plywood is designed to get rained on during framing and then be covered with roofing or siding. It is not exterior-rated plywood.
For permanent exterior exposure, you need plywood with Exteriorrated glue — typically stamped "EXT" or "Exterior." This is a different adhesive formulation that resists long-term moisture without delaminating.
Structural vs Non-Structural Plywood
Structural (sheathing) plywoodcarries an APA span rating and is manufactured to PS 1 or PS 2 structural performance standards. Used for roof sheathing, wall sheathing, subfloor, and any application where the plywood is part of the building's structural system. CDX, OSB, and rated sheathing panels fall in this category.
Non-structural (project/cabinet) plywoodis manufactured for appearance and workability, not structural performance. Hardwood plywood (oak, birch, maple veneer faces), sanded plywood, and shop-grade plywood. Do not use cabinet-grade plywood for structural sheathing — it doesn't carry the required span ratings.
Plywood by Application
| Application | Recommended Grade | Thickness |
|---|---|---|
| Roof sheathing | CDX or rated sheathing | 15/32" or 19/32" |
| Wall sheathing | CDX or rated sheathing | 15/32" |
| Subfloor | T&G rated sheathing | 23/32" |
| Underlayment | Sanded, A-C or B-C | 1/4" or 3/8" |
| Cabinet cases | A-B or B-B sanded | 3/4" |
| Cabinet doors | A-A hardwood | 3/4" |
| Shelving | A-B or B-B sanded | 3/4" |
| Concrete forms | B-C or HDO overlay | 5/8" or 3/4" |
| Exterior siding | T1-11 or A-C Exterior | 5/8" or 3/4" |
| Furniture | A-A or A-B hardwood | 3/4" |
Sheet Sizes
Standard plywood sheets are 4 feet × 8 feet (48" × 96"). Other sizes:
- 4' × 4' — half sheets, common in hardwood plywood and project panels
- 4' × 10' — available in sheathing grades for tall wall applications
- 5' × 5' — Baltic birch standard size (metric 1525mm × 1525mm)
Plywood Weight Per Sheet
Approximate weights for standard softwood (fir) plywood at typical moisture content. Hardwood plywood is slightly heavier; Baltic birch is noticeably heavier at the same thickness.
| Thickness | 4×8 Sheet Weight |
|---|---|
| 1/4" | 22 lbs |
| 3/8" | 28 lbs |
| 1/2" | 40 lbs |
| 5/8" | 48 lbs |
| 3/4" | 60 lbs |
| 1" | 70 lbs |
| 1-1/8" | 80 lbs |
FAQ
What thickness plywood for subfloor?
23/32" (3/4" nominal) tongue-and-groove is the standard for 16" on-center joist spacing. For 24" o.c. joist spacing, use 1-1/8" T&G rated for the wider span. Never use 1/2" plywood as a structural subfloor — it doesn't have the stiffness to prevent floor bounce and squeaks.
What's the difference between plywood and MDF?
Plywood is made from thin wood veneers and has real wood grain, good screw-holding strength, and structural capacity. MDF (medium-density fiberboard) is made from wood fibers and resin pressed into a uniform panel — heavier, no grain direction, machines beautifully with routers, but has poor edge screw-holding, swells catastrophically when wet, and has zero structural capacity. Use MDF for painted cabinet doors and molding profiles; use plywood for anything structural and anything that might see moisture.
Is thicker plywood always stronger?
For a given grade and span rating, yes — thicker plywood is stiffer and stronger. But grade matters too. A 3/4" CDX sheathing panel and a 3/4" A-B sanded cabinet panel may look similar, but the sheathing panel is manufactured to different structural standards. Always match the panel type to the application, not just the thickness.
Can I use plywood outside?
Only if it's rated for exterior exposure. CDX plywood is rated for temporary moisture exposure during construction, NOT for permanent outdoor use. For permanent exterior applications — outdoor furniture, planters, signs, marine use — you need plywood with an Exterior or Marine grade stamp, which uses waterproof adhesive and higher-quality veneers that resist delamination.
Related Calculators & References
- OSB vs Plywood Guide
- Lumber Actual Dimensions
- Roof Area Calculator for sheathing quantities
- Wall Framing Calculator for sheathing sheet count