Deck boards or pavers: how to calculate quantities

A 30 m² deck does not automatically mean buying exactly 30 m² of boards or pavers. Format, laying direction, cuts and packaging turn theoretical area into a purchasing quantity.

Calculate the real area

For a rectangle, area = length × width. A 6.5 m × 4 m deck covers 26 m². For an L-shape, split the plan into rectangles and add their areas.

Boards: area is only the first step

For 26 m² with an 8% allowance:

26 × 1.08 = 28.08 m²

If each pack covers 1.85 m²:

28.08 ÷ 1.85 ≈ 15.18, so 16 packs are needed.

The deck calculator provides a structured estimate, while a cutting plan remains useful when board lengths and joints strongly affect waste.

Pavers: work from effective unit area

A 20 × 10 cm paver covers 0.02 m² theoretically, so there are 50 per m². For 23 m²:

23 × 50 = 1,150 pavers

With 7% allowance:

1,150 × 1.07 = 1,230.5, rounded up before adapting to pallet quantities.

Use the paver calculator to compare formats and allowances.

Waste allowance is project-specific

Cuts, breakage and complex boundaries justify an allowance, but no single percentage suits every layout. Diagonal patterns, curved edges and many obstacles generally create more offcuts than a simple rectangle.

A small post opening should not always be deducted square centimetre by square centimetre: cutting around it can consume nearly as much material as a full area.

Calculate underlying layers separately

A 5 cm layer below 23 m² represents:

23 × 0.05 = 1.15 m³

The gravel calculator can convert volume into mass or packaging assumptions. Screed is a different material system even though its geometry also uses area × thickness; use the screed calculator for that case.

Include drainage geometry

Slope percentage is vertical drop ÷ horizontal distance × 100. A 4 cm drop over 2 m is 2%. The slope calculator converts between drop, distance, percentage and angle; the required slope itself depends on the construction system.

Why layout can change the order

Two projects with the same area can generate different waste. A 4.10 m dimension paired with 4 m boards may require joints or a different cutting strategy. Coverage answers “how much surface?”, while a cutting plan answers “how will available pieces cover that surface?”

Keep separate purchasing lines for finish, support, edging and fixings. An 8% allowance on boards does not imply 8% extra posts or edging.

Before ordering, remeasure, check actual product dimensions and coverage, review packaging and validate support and drainage requirements. For the general method, see planning construction material quantities.