Concrete Slab Calculator

Inputs

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Finished rectangular slab length.
ft
Finished rectangular slab width.
ft
Concrete thickness used for volume only. This calculator does not select slab thickness.
in
Number of identical rectangular slabs.
slabs
Extra concrete for uneven subgrade, form loss, spillage, over-excavation and ordering margin.
%
Concrete volume produced by one bag. A common 80 lb premix bag is about 0.6 ft^3; use the bag label for final buying.
ft³
Ready-mix capacity per truckload, in cubic yards. Use your supplier limit if different.
yd3/truck
Normal-weight concrete is often around 2300-2400 kg/m^3. Use project data if known.
lb/ft³
Optional user-entered ready-mix or budget price per cubic yard. This is not a live price lookup.
$/yd3

Results

Default result
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Total concrete volume
44ft³

Also computed

Concrete yards1.63yd3

Cubic yards after the waste allowance.

Bags to buy74bags

Rounded up from total volume divided by entered bag yield.

Slab area120ft²

Waste / overage volume4ft³

Estimated concrete weight6,318lb

Entered-price cost0.00$

Uses only the entered price per cubic yard.

Method notes 4 notes
  • Base slab volume = length * width * thickness * slab count.
  • Waste or overage is applied before bag count, truckload count and entered-price cost are rounded or estimated.
  • This is a material takeoff only. It does not choose slab thickness, mix design, reinforcement, control-joint spacing, subbase, compaction, vapor barrier, drainage, frost protection or local code requirements.
  • Use the bag label or ready-mix supplier quantity, minimum-load and delivery rules for final ordering.

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