Free Online Quantity Takeoff Calculator: Concrete, Rebar, Formwork

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Concrete is volume, rebar comes from typical reinforcement ratios that you can override per element, and formwork is the contact area of the forms: footing and column sides, beam sides and soffit, slab soffit and edges, both wall faces. Set count to zero to skip a row.

From drawings to the three quantities

Every structural estimate starts the same way: walk the drawings element by element and reduce each one to concrete volume, reinforcement weight, and formwork area. The tool above does the arithmetic for up to five element groups at once. Concrete is length times width times height times count, with a waste allowance on the order quantity. Rebar uses typical reinforcement ratios per element type, from 80 kg per cubic meter in footings to 160 in columns, all overridable when you have bar schedules. Formwork is contact area, computed with the correct geometry for each element type.

Quantity takeoff diagram showing a footing, column, beam, and slab with rebar indicated, and the three quantities of concrete volume, steel ratio, and formwork contact area
Every element reduces to volume for concrete, a steel ratio for rebar, and contact area for formwork.

This opens the Construction Estimator Suite in the bar above, alongside the concrete mix, rebar spacing, and excavation calculators that detail the same quantities further.

Where estimates go wrong

  • Formwork is the classic miss: it often costs more than the concrete it shapes, and slab edges, beam sides, and column forms hide from anyone measuring only volumes.
  • Reinforcement ratios are honest averages: heavily loaded transfer beams can double the typical figure, which is why the ratio is editable per row.
  • The waste allowance covers spillage, over-excavation, and pump line losses: 5 percent is normal, more for thin slabs on rough ground.
  • Counting is the discipline: the calculator multiplies faithfully, so the estimate is only as good as the element count from the drawings.

What this tool is for

Pricing small structures, sanity-checking a subcontractor's quantities, and teaching the takeoff logic that commercial estimating software automates. The output feeds directly into the bill of quantities builder in this suite.

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