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Concrete Calculator
Adjust slab dimensions and watch volume, materials, and cost update instantly.
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Adjust slab dimensions and watch volume, materials, and cost update instantly.
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Practical notes to help you use this tool confidently — scan the sections below or explore related calculators.
Estimate concrete volume for rectangular slabs from length, width, and thickness. Results update live as you adjust dimensions, with a scaled preview of slab proportions.
Outputs include cubic volume, an approximate cement bag count, and a rough cost estimate for early planning.
Volume is calculated as length × width × depth, converted to a consistent unit internally (meters), then displayed in metric or imperial based on your settings.
Cement bag estimates assume a typical mix ratio for general-purpose slabs. Always confirm with your supplier for structural or load-bearing work.
Mixing units without converting — always double-check thickness (depth) is not entered in centimeters when you meant meters.
Forgetting waste — site conditions, spillage, and uneven subgrade often require 5–10% extra material.
Using too thin a slab for the load — driveways and garages usually need greater thickness than garden paths.
A 3 m × 2 m patio at 100 mm thick needs about 0.6 m³ of concrete — roughly 2–3 bulk bags or a small ready-mix load depending on packaging.
A 6 m × 6 m garage slab at 150 mm thick is about 5.4 m³ — often a single ready-mix truck for residential projects.
Prepare the subgrade and consider a compacted gravel base before pouring — the visual preview shows slab thickness relative to a base layer.
Order slightly more than calculated; returning unused material is harder than a short pour mid-project.
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Quick answers for common planning questions.
Multiply length × width × thickness (all in the same unit) to get volume. This calculator handles unit conversion and shows volume in m³ or cubic feet depending on your settings.