Concrete Calculator
Estimate slab concrete volume from length, width, and depth. Add a waste allowance and optional density, bag yield, and pricing for your project.
Estimate a rectangular slab. Enter the material density from your supplier if you need weight; no density is assumed.
Concrete estimate
Enter length, width, and depth to estimate volume. Add density, pricing, or bag yield when you have those details.
Volume = length × width × depth × (1 + allowance ÷ 100). Weight = volume × the density you supply. Cost = volume or weight in the selected pricing unit × unit price.
Bags = volume including allowance ÷ volume yield per bag, rounded up to the next whole bag.
1 yd³ = 27 ft³. A metric tonne is 1,000 kg; a US short ton is 2,000 lb. These estimates exclude delivery, labor, taxes, and minimum-order fees. Confirm the required mix and structural design separately.
How to use Concrete Calculator
- Enter the rectangular slab's dimensions and choose the appropriate units.
- Set a waste allowance if needed; optionally supply density, bag yield, and a unit price.
- Calculate required volume, plus weight, whole bags, or cost when their inputs are available.
What is Concrete Calculator?
A slab's geometric volume is length × width × depth. A waste allowance increases that volume by the entered percentage. Weight requires a material density, and bag count requires the finished volume yielded by each bag. Those product-specific values are entered explicitly instead of being guessed from a bag's dry weight.
- Cubic meters, feet, and yards
- Explicit waste allowance
- Optional density and whole-bag estimate
- Volume- or weight-based cost calculation
A practical example
20 ft × 20 ft × 6 in Waste allowance 0%
200 ft³ Approximately 7.4074 yd³ · 5.6634 m³
Frequently asked questions
How many bags do I need?
Enter the finished concrete yield per bag in a supported volume unit. The required volume is divided by that yield and rounded up to a whole number of bags.
What density should I enter?
Use the density specified for your material or supplier. Without a density, the tool reports volume and does not invent a weight estimate.
Is a waste allowance automatically included?
No. The default is zero percent. Enter an allowance appropriate to your project; it is applied once to the geometric volume.