Free · Concrete & masonry

Concrete Slab Volume & Material Calculator

Estimate concrete volume and material quantities for the selected slab form.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

Enter the values you know

Results update as you type. Edit a result to calculate another value, or lock a value to keep it fixed.

Choose a concrete form
Dimensions
pieces
Pre-mixed concrete
%
Costs
/bag
/piece
/
/
Result

Your calculation

Enter enough known values to calculate the blanks.

Use one currency for your figures. Mixed-currency conversions use rates captured October 5, 2026, rather than live exchange rates.

How to use this calculator

  1. Enter the values you know in the units shown. Leave unknown values blank.
  2. Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
  3. Reset restores the starting fields. A worked example appears below.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

For a rectangular slab, multiply length, width and depth to obtain volume. The selected form, mix, quantity and allowance determine the additional material estimates shown.

Slab volume = length × width × depth × quantity; mass = volume × density; bags = mass × (1 + waste fraction) ÷ bag mass. Other form choices use their displayed dimensions.

Worked example

Enter these known values and leave the other values blank.

Concrete form
Slab
Length
5 m
Width
4 m
Height/depth
10 cm
Quantity
1 pieces
Density
2400 kg/m³
Bag size
25 kg
Waste
0 %
Total area
20 m²
Volume
2 m³
Weight
4800 kg
Bags needed
192

Assumptions and limitations

  • Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.
  • Currency conversions use the captured source rates from October 5, 2026; they are not live exchange rates.

Common questions

What does this concrete slab calculation tell me?

For a rectangular slab, multiply length, width and depth to obtain volume. The selected form, mix, quantity and allowance determine the additional material estimates shown.

Can I calculate a different unknown?

Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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