Concrete & masonry
Concrete Slab Calculator
Enter the slab length, width and thickness to estimate concrete volume for a slab, pad, patio, driveway, floor or sidewalk. Add only the extra allowance you want to use.
YOUR MATERIAL ESTIMATE
A clearer quantity starts here.
Enter your measurements, check the units and calculate. Your result will include the assumptions and rounding steps.
Show calculation
THE WORKFLOW
How to use this concrete slab calculator
- Enter slab length, width and thickness.
- Confirm measurement units and the number of slabs.
- Add optional waste and calculate; compare net volume with order volume.
Formula & assumptions
Slab volume = length × width × thickness × quantity. Order volume = net volume × (1 + waste / 100).
Constant thickness and rectangular slabs are assumed. Dimensions describe quantity, not structural suitability. Convert all lengths to matching units before multiplying. One cubic yard is 27 cubic feet. Bag equivalents use the editable product yield.
See methodology and sources →AN ARITHMETIC EXAMPLE, NOT A RECOMMENDATION
Worked example
Example only: one 10 × 10 ft slab with an entered thickness of 4 in, no extra.
- Project area100 ft²
- Project area9.29 m²
- Net volume1.235 yd³
- Order volume1.235 yd³
Example calculation
Geometry: base area 9.290304 m² × depth 0.1016 m × quantity 1 = 0.943895 m³.
Extra: 0.943895 m³ × (1 + 0 / 100) = 0.943895 m³. Conversion: divide m³ by 0.764554857984 to obtain yd³.
Bags: 33.333333 ft³ ÷ 0.6 ft³ per bag = 55.555556; round up to 56.
Common questions
Does this choose dimensions for my project?
No. Enter dimensions from your project plan. The calculator measures quantity, not structural suitability.
How much extra should I enter?
Use the allowance appropriate to your measurements, project conditions and supplier. The field is editable; there is no universal waste percentage.
Estimates only. Verify measurements and manufacturer packaging/yields. Project conditions vary. This tool does not provide structural engineering advice. Read the disclaimer.