October 2026

7/8-Inch Baltic Birch Plywood: What 21 mm Means

Understand how Berta Store’s current 21 mm BB/BB Baltic Birch panel relates to the 7/8-inch label, then plan joinery, hardware and handling.

Metric-to-inch selection

Quick answer

Berta Store’s current 7/8-inch Baltic Birch option is listed at 21 mm, which converts to approximately 0.827 inch—not an exact 0.875 inch. The current 4×8 BB/BB variant is listed with 15 plies, a solid-birch core, unfinished faces on both sides and WBP glue.

The extra material can be useful for robust cabinet parts, furniture components, deep joinery and projects where a thicker exposed multi-ply edge is part of the design. It does not create a universal load rating. Measure the delivered panel and verify hardware, groove and machine clearances before cutting.

21 mmCurrent listed metric thickness of the 7/8-inch variant.

≈ 0.827 in.Mathematical conversion of 21 mm.

15 pliesCurrent listed ply count for this specific Berta variant.

Main takeaway: “7/8 inch” is the nominal shopping label; 21 mm is the listed specification. Use an actual sheet measurement for joinery and tooling.

The conversion

21 mm is close to 7/8 inch, but not equal

Label or value	Millimeters	Inches	Difference from 21 mm	Use in the shop
Berta 3/4-in. BB/BB variant	18 mm listed	≈ 0.709 in.	3 mm thinner	Common cabinet-panel reference; measure before machining.
Berta 7/8-in. BB/BB variant	21 mm listed	≈ 0.827 in.	Reference	Use the delivered material to establish actual joint dimensions.
Exact 7/8 inch	22.225 mm	0.875 in.	1.225 mm thicker	Do not assume this is the measured Berta sheet.
Exact 1 inch	25.4 mm	1.000 in.	4.4 mm thicker	Not interchangeable with the 21 mm panel.

18 mmCurrent nominal 3/4-in. reference

21 mmCurrent nominal 7/8-in. panel

22.225 mmExact mathematical 7/8 in.

This graphic compares numeric thicknesses only; it is not a tolerance drawing. Berta’s Baltic Birch thickness chart provides the broader family, while the actual plywood thickness chart explains why nominal names and measured panels should be kept separate.

Application logic

Where 21 mm can earn the extra thickness

Furniture and exposed edges

A 21 mm, 15-ply BB/BB panel creates a visually substantial multi-ply edge. That can be a design feature in benches, tables, desks and shop furniture when the edge is machined and finished deliberately.

Robust cabinet components

Thicker sides, partitions or structural panels can provide more material around dados and fasteners. The joint still needs enough remaining wall thickness, suitable fasteners and project-specific validation.

Shelves and spans

Moving from 18 to 21 mm can reduce deflection in an otherwise comparable panel, but no span or capacity follows from thickness alone. Load, width, depth, grain direction, edging and support placement remain decisive.

For shelf planning, use the plywood shelf material and support reference. For general material identity and grade terminology, use what Baltic Birch plywood is.

Machining checks

What changes when the panel is thicker

Shop decision	Check before production	Why it matters
Dados and rabbets	Measure the sheet; choose depth that leaves adequate material; cut a full joint sample	A deeper joint can remove more wall thickness than expected.
CNC toolpath	Confirm flute length, stick-out, pass depth, workholding and spoilboard clearance	A tool that clears 18 mm may not provide the same safe cutting envelope at 21 mm.
Hinges and slides	Verify the exact hardware model, cup/boring depth, screw length, setback and cabinet geometry	Hardware dimensions are model-specific; thicker material does not automatically solve compatibility.
Edge treatment	Decide whether the 15-ply edge stays visible, receives finish, or is covered	The choice changes part dimensions, sanding and assembly sequence.
Machine capacity	Check blade height, cutter reach, dust extraction and feed support	Full 4×8 handling and cut depth both affect safety and finish quality.

Weight and logistics

Expect more sheet weight, then verify it

If construction and density were otherwise identical, a 21 mm panel contains about 16.7% more material by thickness than an 18 mm panel. Real sheet weights can still differ because panel construction, moisture and manufacturing vary, so that ratio is a planning comparison—not a published Berta weight.

Handling

Plan enough help or lifting equipment for a full 4×8 sheet. Verify panel carts, storage racks, saw infeed and outfeed before the shipment arrives.

Cut yield

Use the plywood cut-list calculator, then add trim, kerf and defect allowances. Thickness does not change sheet area, but it can change which parts are assigned to the panel.

Delivery

Use the plywood delivery calculator for planning, and confirm unloading, access and site conditions separately.

The plywood weight planning chart is useful for context, but a current product or shipment value is needed when a precise handling or freight calculation matters.

Current 21 mm panel

BB/BB Baltic Birch in the 7/8-inch category

Stacked 21 millimeter BB/BB Baltic Birch plywood sheets in a 4 by 8 format

Current listed construction

The selected variant is listed at 4×8 feet (1220 × 2440 mm), 21 mm, BB/BB, 15 plies, solid birch core, unfinished on both sides and WBP glue. Those details apply to this product variant, not every panel sold as 7/8-inch plywood.

Check the 21 mm variant

Close view of the 15-ply edge on 21 millimeter BB/BB Baltic Birch plywood

Inspect the edge and faces

Use the edge detail to plan exposed-ply aesthetics, sanding and finishing. Before cutting, confirm the delivered sheet’s actual thickness, face appearance, flatness and suitability for the final environment.

View the 7/8-inch 4×8 category

Frequently asked questions

21 mm Baltic Birch questions

Is 21 mm plywood the same as 7/8 inch?

It is the current nominal category, but it is not an exact conversion. Twenty-one millimeters is approximately 0.827 inch; exact 7/8 inch is 22.225 mm. Measure the sheet for machining.

How much thicker is 21 mm than 18 mm plywood?

The listed difference is 3 mm, or approximately 0.118 inch. That is about 16.7% more thickness relative to 18 mm, but it does not by itself establish a capacity increase.

Can 21 mm Baltic Birch be used for shelves?

It can be considered for shelves, but the acceptable span depends on depth, width, load, grain direction, edge treatment, supports and deflection criteria. No universal span is claimed here.

Does this panel have 15 plies?

The current Berta 21 mm BB/BB variant is listed with 15 plies. Do not apply that count to another product, thickness or supplier without checking its specification.

Does WBP glue make the panel exterior plywood?

No exterior-use claim is made here. Glue classification alone does not establish that the complete panel is suitable for exterior exposure. Verify the panel’s full specification and environmental requirements before specifying it for moisture exposure.

Selection and takeoff

Continue the 21 mm project plan

Bottom line: shop this panel as 21 mm, not as an assumed exact 0.875 inch. Verify the delivered material, hardware and tool clearances before production.