MEASURE ONCE. PLAN YOUR PURCHASE.

Formwork calculator.

Estimate the board length and face area around a rectangular pour.

CONCRETE

Your inputs

Measurement schematic, not to scale. Use your own dimensions and product specification.

Use measurements from your plan and properties from your chosen product. Any prefilled values are illustrative.

Length

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Width

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Form face height

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Purchased board length

Where to get this value

Use the actual usable quantity or dimensions of the product you intend to buy. Check the label and the unit shown here.

Waste allowance

Shortcuts only; choose your own allowance above.

Where to get this value

Enter your own allowance. Presets are input shortcuts, not a construction recommendation.

YOUR ESTIMATE

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A clear estimate starts here.

Enter your dimensions and product details to see the quantity and purchase breakdown.

KEEP YOUR PROJECT TOGETHER

Plan the full project.

Reuse your dimensions, add the other materials and build a purchase list.

Open Concrete slab project

Formula and assumptions

BEHIND THE NUMBERS

How this calculation works.

Purchase count is based on total board length and your allowance. It does not optimise cuts or specify bracing, joints or structural capacity.

Perimeter = 2 × (L + W)Calculated with normalised units

A worked example

Illustrative inputs only. Product properties and design dimensions are not recommendations for your project.

Length: 4 m
Width: 5 m
Form face height: 100 mm
Purchased board length: 3 m
Waste allowance: 10 %

Form boards: 7 boards

Before you purchase

Use dimensions from your plan and properties from your chosen product. Any design spacing, section or fixing pattern must already be specified.

Method: dimensional arithmetic and user-supplied specifications. Software checks: 2026-10-03. Calculation and review policy.

Check your purchase assumptions

Choose which concrete faces belong in form contact area Separate form contact area from concrete volume

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Explore form faces, mesh and specified reinforcement

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Prepare your material measurements and product data

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Find material sheets for this calculator

Compare supplied alternatives and quantity changes

Browse all quantity scenarios

Formwork calculator.

Your inputs

A clear estimate starts here.

Plan the full project.

How this calculation works.

A worked example

Before you purchase

Check your purchase assumptions

Keep the project moving.

Connected work guides and comparisons

Prepare your material measurements and product data

Compare supplied alternatives and quantity changes