Plywood Thickness: Chart, Actual Sizes and Fit Checks
Use a plywood thickness chart without mistaking a label for a measurement. Check actual stock, test grooves and calculate clear openings before cutting.
Alexander Novak Updated 14 October 2026 11 min read
Plywood thickness: use the label to buy and a measurement to cut
Plywood thickness is sold by a nominal size or a stated metric size, but the actual sheet can differ from that label. Measure your delivered plywood before sizing grooves, cabinet openings or fitted parts; a conversion chart cannot replace that check.
The important distinction is not just thick versus thin. It is the size on the order versus the size that your joint must accept. Keep both in the material record. A label helps you find the product; a measured value helps you make it fit.
The workshop photographs in this guide are AI-generated editorial images, not CarpDraw results or measured product samples. The diagrams are drawn in code from the stated numbers.
Once the thickness is recorded, use the cabinet plywood buying guide to specify the face, core, grade and finish separately.
Plywood thickness chart: labels and exact conversions
These are exact conversions of thickness labels, not guaranteed actual sizes, manufacturing tolerances or load ratings. Availability depends on the supplier and panel family. Millimeters are included because plywood is often specified in mm; centimeters make the same dimensions easier to compare with furniture drawings.
| Thickness label in inches | Exact mm conversion | Exact cm conversion | What the number tells you |
|---|---|---|---|
| 1/8 in | 3.175 mm | 0.3175 cm | Conversion of the inch label only |
| 1/4 in | 6.35 mm | 0.635 cm | Conversion of the inch label only |
| 3/8 in | 9.525 mm | 0.9525 cm | Conversion of the inch label only |
| 1/2 in | 12.7 mm | 1.27 cm | Conversion of the inch label only |
| 5/8 in | 15.875 mm | 1.5875 cm | Conversion of the inch label only |
| 3/4 in | 19.05 mm | 1.905 cm | Conversion of the inch label only |
| 7/8 in | 22.225 mm | 2.2225 cm | Conversion of the inch label only |
| 1 in | 25.4 mm | 2.54 cm | Conversion of the inch label only |
A panel marked 23/32 in has an exact label conversion of 18.25625 mm, or 1.825625 cm. That is 1/32 in, or 0.79375 mm, less than an exact 3/4 in. It is not proof that every sheet sold as nominal 3/4 in measures 23/32 in.
Likewise, 18 mm means 1.8 cm, or about 0.7087 in. It is not the exact metric equivalent of 3/4 in. If a drawing calls for one and a supplier offers the other, treat it as a material substitution and review the affected dimensions.
The Canadian Wood Council's plywood sizes reference provides a useful regional size reference. Use the supplier's documentation for your particular panel rather than treating a general chart as its certificate.
How do you measure actual plywood thickness?
Use calipers across two clean, opposite faces near an accessible edge, then repeat at several locations and on more than one sheet. Record the range, not just a convenient single reading. Do not squeeze the jaws hard enough to compress the face or measure over edge debris.
How to check plywood thickness before cutting
- Identify the batch
Keep the product label, supplier name and nominal size with the material. Separate sheets from different products or deliveries before measuring.
- Check the instrument
Clean the caliper jaws, close them gently and check zero. Use an instrument whose accuracy suits the joint you intend to make; extra decimal places on a screen do not prove extra accuracy.
- Measure opposite faces
Place the outside jaws squarely across the thickness. Avoid a damaged corner, a loose splinter, an edge-band overhang or a local finish drip. Move to another sound spot if the reading is unstable.
- Sample several positions
Measure accessible positions around each representative sheet. A short-jaw caliper cannot check the middle of a full sheet. If variation across the sheet matters to the job, agree a suitable inspection method with the supplier or maker.
- Record before machining
Write the minimum and maximum readings, units, sheet identification and whether you measured a coated or unfinished panel. Make a test joint from the actual material before committing the finished parts.
For a pocket-screwed cabinet joint, take those measured values to the pocket screw length reference and check the thin-stock exceptions before drilling.
For straight-through fastenings, use the wood screw length and tip-clearance example with your measured panel thickness, not the nominal sheet label.
A tape measure is useful for sheet length and width, but it is a poor choice for a close-fitting groove. Nor should you stack several sheets, measure the stack and assume every sheet equals the average. One thick and one thin panel can hide inside the same total.
Eight thickness labels at the same visual scale
This gallery changes only the thickness dimension. All eight diagrams use the same viewing scale and panel width, so they show the relative difference between exact inch labels without changing species, finish or camera angle. These are mathematical profiles, not photos of stocked sheets and not a recommendation to use a particular size.
Gallery8 photos · tap to enlarge
Fit the groove to the panel, not the router bit's name
For a dado or groove, the critical dimension is the actual mating part and the intended joint fit. A cutter marked 3/4 in does not automatically make the right groove for nominal 3/4 in plywood. The panel, tool, machine setup and cutting process can all affect the result. For a worked fitting sequence, follow the dado joint test-cut and dry-fit method before machining your finished cabinet sides.
I would make a test groove in a scrap from the same batch before cutting a cabinet side. Test the actual mating piece, not a different offcut that merely looks similar. Follow the adhesive and joint design requirements; there is no single extra clearance that fits every plywood joint.
If the fit is too tight, forcing the panel can damage the thin face veneer or push the assembly out of square. If it is too loose, the result can be a visible gap and a joint that does not behave as designed. Glue is not a general cure for a badly matched groove.
Keep the successful test block with the material until the job is finished. It is a simple physical reference if a setup changes or another person takes over. When a new sheet arrives, repeat the check instead of assuming it matches yesterday's supply.
Calculate openings from the measured side thickness
For two sides inside a fixed overall width, the basic clear-opening calculation is overall width minus left-side thickness minus right-side thickness. It describes the clear space only. Joint allowances, drawer-slide requirements and other fitted parts need their own dimensions.
Consider an illustrative box that is 600 mm wide overall, or 60 cm and about 23.622 in. If each side is exactly 18 mm thick, the opening is 600 - 18 - 18 = 564 mm, or 56.4 cm and about 22.205 in.
If each side were exactly 19.05 mm instead, that opening would become 561.9 mm, or 56.19 cm and about 22.122 in. The 2.1 mm difference, about 0.083 in, is large enough to matter to a fitted component. These values illustrate the arithmetic; they are not measurements of a supplied sheet.
The same issue appears in shelving. A fixed overall case width does not tell you the shelf length until you know the sides and joints. Our bookshelf measurement guide explains the separate role of overall size and usable shelf space.
Do not extend the arithmetic into a strength claim. A shelf's suitable thickness also depends on its span, intended load, support arrangement, panel construction and deflection limit. APA's plywood overview explains the engineered panel product; the grade and design information for the actual panel still matter. A thicker label alone is not a safe-load table.
Keep one thickness record from purchase to handoff
A small thickness error becomes expensive when it is copied into every part. Keep one source of truth for the delivered batch, then revise each dependent dimension from it. Do not fix a fit problem by quietly changing a drawing while the cutting list still contains the old number.
| Record item | Example or action | Status to show |
|---|---|---|
| Product and supplier | Copy the exact product description | Documented |
| Nominal thickness | Copy the order or panel label | Specified, not measured |
| Actual thickness | Enter your minimum and maximum caliper readings | Measured, with date and units |
| Surface condition | Note unfinished, factory coated or shop finished | Observed |
| Groove fit | Keep the approved test piece and setup note | Tested on this batch |
| Openings and fittings | Recalculate from the accepted material | Checked by the maker |
| Replacement sheets | Recheck before mixing into the job | Pending until measured |
Three shortcuts to avoid: using a nominal dimension in a precision joint, rounding a metric panel to a familiar inch fraction, and buying a replacement sheet after machining without rechecking it. The cost is usually remaking a part, not merely correcting a number in a notebook.
Do not confuse this measurement decision with selecting the panel material. If you are still choosing between board products, read MDF versus plywood for furniture separately. A thickness reading cannot identify hidden core construction or establish fastener performance.
The full manual handoff is straightforward: attach a clear panel-edge photo, label the supplier and batch, record your measurements, show the joint test and list the dimensions that depend on thickness. Its weak point is revision control when a new sheet or supplier enters the project.
If you explore CarpDraw's furniture planning entry point, keep that verified material record with your reference information. The current drawing provider is not available for reliable drawing generation. CarpDraw cannot measure a panel from its photo, approve a shelf load or replace the maker's fit check.
Project brief
Workshop note: use the specified plywood product and approved batch. Actual thickness remains a measured field, not a photo estimate. Confirm the joint sample and update openings before releasing fitted parts for cutting. Any replacement sheet triggers a fresh thickness check.
Frequently asked questions
Is 1/2 inch plywood really 1/2 inch thick?
Not necessarily. Exactly 1/2 in converts to 12.7 mm or 1.27 cm, but a nominal retail label does not establish the actual sheet measurement. Check the product documentation and measure the delivered stock before cutting a matching joint.
Is 5/8 inch plywood actually 5/8 inch thick?
Do not assume it is. The exact conversion of 5/8 in is 15.875 mm or 1.5875 cm, while the supplied product has its own stated dimensions and permitted variation. Use a caliper reading for fitting and the manufacturer's specification for purchasing acceptance.
Is 3/4 plywood actually 3/4 inch thick?
It may not be an exact 0.75 in or 19.05 mm sheet. Products sold in that nominal category can use other stated dimensions, and an 18 mm panel is a different exact size. For 3/4 plywood actual thickness, use the delivered sheet's measurement rather than one universal internet value.
What is thicker plywood, 23/32 or 3/4?
As exact fractions, 3/4 in is thicker by 1/32 in, equal to 0.79375 mm or 0.079375 cm. That compares the numbers, not two physical sheets. Nominal labels and manufacturing variation mean you should measure the products before judging their fit.
Is 3/4 plywood stronger than 1/2 plywood?
For otherwise comparable panels, greater thickness generally improves bending stiffness, but that does not establish an allowable load for your assembly. Construction, grade, span, orientation and supports also matter. Do not use this thickness chart as a structural design guide.
Is 1 inch plywood actually 1 inch thick?
An exact inch is 25.4 mm or 2.54 cm, but a product sold under a nominal 1 in label must still be checked. Ask the supplier for its stated thickness and tolerance, then measure the material if fit matters. Do not infer thickness from a photograph or layer count.
Co-founder, architect
Alexander is a co-founder of CarpDraw and a practising architect. He prepares technical drawings for his own projects, so he runs into the same problem every week: turning a furniture idea or a reference photo into drawings and specifications a maker can actually build from. CarpDraw is the tool he wanted for that work, and he writes here about drawings, dimensions and getting furniture from idea to build.
