Formwork area is the concrete surface in contact with the form. A slab is its soffit plus edges (L × W + 2(L + W) × t); a beam is its soffit plus both sides below the slab; a column is its perimeter × height. A 6 × 5 m slab 200 mm thick needs 30 + 4.4 = 34.4 m², or 13 sheets with 10% waste.
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Formwork Area Calculator
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Formwork area to order
37.84m²
Net contact area
34.40 m²
Sheets
13 sheets
Per element (before openings)
34.40 m²
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Generated with myconstructioncalculator.com. Estimates for planning and ordering only; verify against drawings and specifications.
Formulas
Element
Formwork area
Slab
L × W + 2 × (L + W) × t
Beam
b × L + 2 × d × L (d = depth below the slab)
Column
2 × (b + d) × H
Wall
2 × L × H + 2 × t × H (faces + ends)
Footing
2 × (L + W) × D (sides only)
Then: net area = (area − openings) × number of elements; order area = net × (1 + wastage %).
Worked Example
A suspended slab 6 × 5 m, 200 mm thick, 10% wastage, 1220 × 2440 mm sheets:
Soffit = 6 × 5 = 30.00 m²
Edges = 2 × (6 + 5) × 0.2 = 4.40 m²
Net = 34.40 m²; with 10% = 37.84 m²
Sheets = ⌈37.84 ÷ 2.98⌉ = 13 sheets
Formwork Area per Cubic Metre of Concrete
A useful rule for estimating and checking take-offs:
Element (typical size)
Formwork m² per m³
Slab 200 mm
≈ 5.0 (soffit only)
Beam 300 × 600 mm (450 below slab)
≈ 6.7
Column 400 × 400 mm
10.0
Wall 200 mm
10.0
Footing 2 × 2 × 0.6 m
2.0
Assumptions
Contact area only; it excludes props, bearers and bracing.
Beam depth is measured below the slab soffit; the beam’s top within the slab is not formed.
Footing area is the sides only: the base sits on blinding.
Frequently Asked Questions
How do I calculate shuttering area for a slab?
Soffit area (length × width) plus the edge forms (perimeter × slab thickness). Deduct openings larger than your measurement rule allows, often 1 m².
How is a beam measured in the formwork area?
As its soffit (width × span) plus two sides, each the depth below the slab × span. The part of the beam within the slab depth is left out, because the slab soffit form already covers it.
How do I calculate column formwork area?
Perimeter × height, 2 × (width + depth) × height. A 400 × 600 mm column 3 m high is 2 × 1.0 × 3 = 6 m².
How many plywood sheets do I need?
Divide the area (with wastage) by the sheet area (2.98 m² for 1220 × 2440 mm or 32 ft² for 4 × 8 ft) and round up.
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