Construction
Concrete Slab Calculator
Estimate concrete for one or several slabs, add a visible waste allowance and compare ready-mix volume with whole bags. Edit the actual product yield before using a bag estimate.
Turn project dimensions into an order quantity.
Inputs
Enter 0 to omit cost; use your local currency.
Calculated locally in your browser. No sign-up or input upload.
Results
Concrete including waste
1.575 m³2.06 yd³55.621 ft³Total slab coverage
15 m²161.459 ft²Area per slab
15 m²161.459 ft²Net concrete volume
1.5 m³1.962 yd³52.972 ft³Whole bags required
93 bagsDry bag purchase weight
3,374.727 kg7,440 lbMaterial breakdown
- Concrete bags
- ceil(1.575 m³ / 0.01699 m³ per bag) = 93
Assumptions & checks
This is a quantity estimate. It does not specify structural slab thickness, reinforcement, mix strength or foundation design. Bag yield is product-specific.
Formula
Order concrete by volume; package counts use finished concrete yield, not dry bag volume.
Worked example
Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.
Inputs
- Project shape
- Rectangle
- Project length
- 5 m
- Project width
- 3 m
- Slab thickness
- 100 mm
- Number of slabs
- 1
- Waste allowance
- 5 %
- Dry bag weight
- 80 lb
- Finished concrete yield per bag
- 0.6 ft³
- Supplier price (optional)
- 0
- Price per
- m³
Result
- Concrete including waste
- 1.575 m³
- Total slab coverage
- 15 m²
- Area per slab
- 15 m²
- Net concrete volume
- 1.5 m³
- Whole bags required
- 93 bags
- Dry bag purchase weight
- 3,374.727 kg
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Frequently asked questions
Why is bag yield editable?
Finished yield depends on the packaged product. The included 60 lb and 80 lb presets refer to QUIKRETE No. 1101, and should be replaced when you use another mix.
Does waste change slab thickness?
No. Waste increases order volume. Reverse coverage removes that allowance from the available quantity, then divides the remaining concrete by the entered thickness.
Reference data & method sources
- QUIKRETE Concrete Mix No. 1101 data sheet
Approximate yield: 80 lb = 0.60 ft³; 60 lb = 0.45 ft³. Edit for your product.