Actual plywood thickness: 3/4 inch, 23/32 inch and 18 mm

Exact conversions, not guaranteed panel measurements

This table converts numbers. It does not predict a particular sheet’s delivered thickness, tolerance or core. The difference between 3/4 inch and 18 mm is 1.05 mm; between two case sides, that changes the available inside width by 2.1 mm.

Why a small difference changes the parts

Consider a 30-inch-wide case with top and bottom panels fitted between the sides. If each side actually measures 3/4 inch, the horizontal parts are 28 1/2 inches long. If each side measures exactly 18 mm, the same case width of 762 mm leaves 726 mm between them, about 28.5827 inches.

That difference matters when you copy a cut list without checking its assumptions. It also affects where centered end holes sit and how much material remains behind a blind hole. Keep overall dimensions, finished part sizes and drilling coordinates tied to the same measured stock.

How to record a useful thickness measurement

Measure representative places on the actual sheets, away from a damaged edge or obvious defect. Record the thickness in one consistent unit, identify which sheet belongs to which parts, and test the mating joint with an offcut. If faces or edges receive additional treatment, account for when the final fitting happens.

A supplier’s product sheet can explain the construction and tolerance, but a generic face name such as “oak plywood” leaves important details unresolved. Columbia’s core guide describes several panel constructions with different characteristics. Ask for the actual core, face grade and product specification.

Set groove width from the shelf, not the side label

A dado must receive the mating shelf thickness. A 3/4-inch cutter and a shelf cut from a thinner sheet can produce a loose joint. Check the actual finished cut, not just the bit label. Groove depth is a separate measurement into the side; it determines the extra length needed at each shelf end.

Put the measurement into the plan

In Plan Studio, enter actual panel thickness before reviewing parts and machining. The current case templates use one main thickness, so a build with different side and shelf thicknesses requires a separately resolved layout rather than silently mixing sheets.

Read how dado shelf length changes, compare plywood and MDF, or review shelf thickness and support planning. Measuring thickness solves fit; it does not by itself establish shelf capacity.