Birch Plywood Thickness With the Tolerance Printed

October 3, 2026

We publish the thickness tolerance on every sheet we sell. Our 18 mm runs 17.1 to 18.7 mm. Ask the next three suppliers who quote you for their figure and count how many answer.

That is the reason to read this page. The rest is arithmetic: what we list, what the mill will run on request, what a sheet weighs and how many go in a pack. All of it Stiga RM birch plywood from Kuldiga, Latvia, at 1250 x 2500 mm. Grades, certification and the buying constraints sit in the buyer's guide.

What we list, what the mill runs

15, 18 and 21 mm from the standard list. Beyond those the mill runs 6.5 to 40 mm on request, and 6.5 to 35 mm on the film faced grades, where the pressing and the film application set the ceiling. If you need 40 mm it will be an uncoated grade.

	Listed	On request
Uncoated: C/C, CP/CP, BB/CP, BB/BB	15, 18, 21 mm	6.5 to 40 mm
Film faced: F/F, F/W	15, 18, 21 mm	6.5 to 35 mm

Listed does not mean stock. The mill holds none and produces to order, so a listed thickness is one that runs often and needs no discussion. Anything outside the list we confirm at quotation, and it can move the lead time, already up to 3 weeks depending on season. The 1220 x 2440 mm format comes on request too, with its thickness range confirmed at the same time.

Ply count

The veneers are 1.5 mm, birch all the way through. No poplar core, no softwood filler. Divide through and you get around 10 plies at 15 mm, 12 at 18 mm and 14 at 21 mm.

Those are approximate. Sanding takes material off the faces, and the exact layup is a mill specification rather than a published figure. If your job depends on the construction, or on which way the face grain runs against the long edge, we confirm it at quotation.

Each veneer sits at right angles to the one below it, so every layer restrains its neighbours and the panel comes out close to equally strong both ways. The stack mirrors about the centreline, and that is what keeps it flat. With 1.5 mm veneers the count does not always land on an odd number, as 18 mm shows, so the mill balances an even count by pairing veneers at the core.

Unbalance a sheet after it arrives and it cups, worse as the humidity moves. Sand one face and not the other, seal or laminate one side only, rip a wide sheet off centre. Finishes go on both faces, including the hidden one.

The tolerance, published

Nominal	Permitted range	Under nominal	Over nominal	Total spread
15 mm	14.3 to 15.3 mm	0.7 mm	0.3 mm	1.0 mm
18 mm	17.1 to 18.7 mm	0.9 mm	0.7 mm	1.6 mm
21 mm	20.0 to 21.5 mm	1.0 mm	0.5 mm	1.5 mm

We print this table because the mill declares it. Most importers publish nothing at all, and a supplier with no figure is not offering you a tighter panel. He is offering you less information.

The range leans under nominal at every thickness. A nominal 18 mm sheet can arrive at 17.1 mm, 0.9 mm under the number on your drawing, and nothing has gone wrong. A nominal 21 mm can arrive at 20.0 mm. The 18 mm spread covers 1.6 mm, so two compliant sheets out of one delivery can differ by more than a millimetre and a half, and two pairs stacked by close to 3 mm.

That decides the job wherever the panel meets something machined to a fixed dimension. An 18 mm groove cut to nominal is sloppy on a 17.1 mm panel and will not take an 18.7 mm one. A CNC pocket referenced from the top face leaves less material under it than the drawing says. Slot and tab joints are sized to panel thickness by definition, so 0.9 mm is the difference between a press fit and a part that drops out of your hand. Cam and dowel housings, minifix pockets and edge boring positions all reference thickness. Those are the jobs where one batch assembles and the next does not, with compliant sheets both times.

A sample from your own production run

Before you commit a CNC programme, ask us for a sample sheet from the run that will fill your order. Not nominal, not a sheet off last year's load, not a sample from a different pressing. The mill produces your order as a batch, so we can pull material out of it and send it to you to measure and cut. A programme that will machine hundreds of sheets is worth proving on the material it will see.

Then machine the mating part to the panel you measured. Grooves, slots and pockets are cheap to change in a programme. Panel thickness is not. Where the fit is critical and the volume is large, say so at quotation and we will tell you what the mill can hold.

Weights

Thickness	Weight per sheet	Volume per sheet
15 mm	31.9 kg	0.0469 m3
18 mm	38.2 kg	0.0563 m3
21 mm	44.6 kg	0.0656 m3

The mill states these as approximately 32, 38 and 45 kg, and the computed figures agree. Density is around 680 kg/m3, heavy for a panel product, which is why birch holds a screw where lighter panels strip and why a truck of it runs out of payload before it runs out of deck.

None of the three is a one person lift at 1250 x 2500 mm, and the step from 15 to 21 mm adds almost 13 kg a sheet, so labour cost climbs with the thickness. A pack is about 1.5 tonnes, which decides where it can be stood. Sheet counts per truck and per container are in the load guide.

Per pack

Mills ship whole packs. Part packs either are not available or carry a surcharge, so build the order around these numbers.

Thickness	Sheets per pack	m2 per pack	m3 per pack	kg per pack
15 mm	50	156.2	2.34	1 594
18 mm	40	125.0	2.25	1 530
21 mm	35	109.4	2.30	1 562

Volume holds at around 2.3 m3 and weight at around 1.5 tonnes whatever the thickness, because the mill packs to a constant volume and varies the sheet count. So the pack is a predictable unit to ship and the area it covers is not: 156.2 m2 at 15 mm against 109.4 m2 at 21 mm, a difference of about 43%. Divide your area by the m2 per pack figure for your thickness and round up.

Mixed thicknesses in one load

18 mm as the workhorse, some 15 mm and some 21 mm alongside it, one truck. We confirm the mix at quotation. That is one delivery and one freight bill instead of three, and grades mix the same way. The minimum order is still half a truck overall, about 8 packs, roughly 18 m3 or 12.5 tonnes. The mix sits inside it.

What thickness costs

Within one grade the price per cubic metre barely moves across 15, 18 and 21 mm. Per sheet and per square metre climb, because a thicker sheet contains more wood. You are buying more material, not dearer material. Which is why a square metre price quoted without its thickness cannot compare two suppliers. The price guide has the conversion maths, and the price for your market sits on each product page.

Two questions we get asked

Is an 18 mm sheet 18 mm? No. The declared range is 17.1 to 18.7 mm. Ask us for a sample from your run and measure it before you machine anything that has to fit.

What span will an 18 mm shelf take? No span, load, deflection or fastener figure is published for this product and we will not invent one. If the panel carries load we send you the declaration of performance for the exact grade and thickness, EN 636-2S uncoated and EN 636-3S film faced, and your engineer checks against that.

Get a price

Tell us the thickness, the grade, your square metres and the delivery address. You get a pack count, a price, the certificates, and a sample sheet from the run if a programme depends on it. A thickness outside the listed three is a quotation away, and volumes above half a truck price lower.

Request a quote or see the birch plywood range. A job starting next week is a merchant's job and we will say so.

The six grades: BB/BB and BB/CP for visible faces, CP/CP for covered and structural work, C/C for crates and protection, F/F for formwork and F/W for floors and ramps.