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How to count wooden doors and windows

Updated October 11, 2026

Wooden joinery is bought as timber lengths, board sheets and glass. The volume of timber follows from the lengths and the section of each part; the lengths to buy follow from the length of the timber you can get and from how the pieces are cut.

1. The sections come from the joiner

Width and thickness of the frame and leaf timber depend on the species, the finish and the joiner’s practice. They are editable starting values in the tools: replace them with those of your drawings.

2. Volume and lengths

Volume = total length × width × thickness, for the frame and for the leaves; the waste percentage is added. The lengths to buy are the total length with waste divided by the length of one piece, rounded up. A flat door is counted with two skins of board and its frame; a panelled door adds the stiles and rails of the leaf.

Worked example: one window of 120 × 100 cm

Two leaves, frame 7 × 6 cm, leaf timber 5 × 4.5 cm, 4 m lengths, 10 % waste:

Frame 4.40 m; leaves 53 × 86 cm, 5.56 m of timber.
Volume: (440 × 7 × 6 + 556 × 5 × 4.5) ÷ 10⁶ = 0.031 m³, 0.034 m³ with waste.
Lengths: 10.96 m with waste, i.e. 3 lengths of 4 m. Glass: 2 panes of 43 × 76 cm, 0.72 m² with waste.

Cutting with little waste

Once you know the pieces, the cutting optimiser lays them out on the bars or sheets you buy, with the saw kerf, and shows how many to buy and what is left. It is a heuristic: it gives a good, valid plan and the lowest number any plan could reach, not a proof of the optimum.

What this does not cover

The count does not design the joinery: species, grade, moisture, finish, thermal performance, glazing and hardware are the joiner’s choices.

General information, checked at the date shown. It does not replace advice from a professional for your situation.

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Tools for this guide

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Wood Joinery Quantities

Wooden doors, windows and boards (decking, cladding): timber volume and lengths, board sheets and glass, from your dimensions.

BUILNORA

Cutting Optimizer

Plan the cuts of bars, profiles, boards and rebar, or of sheets and panels, to buy fewer lengths and waste less.

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