Estimated materials—Enter your measurements to calculate.
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Concrete Calculator
Estimate concrete volume for slabs, patios, footings and pads, including an adjustable waste allowance.
How to use this calculator
Enter the actual measurements for the work area, choose the correct unit system, add a reasonable waste allowance, then calculate. For materials sold only in whole bags, boxes, sheets or panels, round up to the next full unit.
Improve the estimate
Read the measurement guide before ordering material.
How to Measure a Concrete Slab for Material Estimating →How the estimate works
Multiply length × width × thickness to get volume, then add the selected waste allowance. The calculator converts the result into cubic yards or cubic meters.
Planning example
A 10 ft × 12 ft slab at 4 in thick is about 1.48 cubic yards before waste. With 10% extra, plan for about 1.63 cubic yards.
Last updated: August 25, 2026
What this calculator includes
This calculator estimates the concrete volume for a rectangular slab, pad, footing or patio. It uses the finished length and width of the pour, the concrete thickness, and your selected extra-material allowance. For US measurements, the result is shown in cubic yards because ready-mix concrete is commonly ordered that way. The same volume is also useful when comparing bagged concrete quantities.
Measurement tips
Measure the inside dimensions of the formwork rather than the outside edges. Check thickness in several places if the subgrade is uneven. A slab that is designed to be 4 inches thick can consume noticeably more concrete if the base has low spots. For irregular shapes, divide the project into smaller rectangles, calculate each one separately, then add the volumes together.
Choosing a waste allowance
A small allowance helps cover spillage, uneven excavation, form movement and small measuring errors. Ten percent is a common planning starting point for a simple pour, but the right number depends on the job. Large, accurately formed slabs may need less; small or irregular pours often benefit from more margin.
Common estimating mistakes
- Entering slab thickness in feet when the form expects inches
- Ordering exactly the theoretical volume with no allowance
- Using outside form dimensions instead of the actual pour dimensions
- Ignoring thickened edges, grade beams or deeper footings
Before you buy
- Confirm whether your supplier sells by cubic yard, cubic meter or bag count
- Ask about minimum ready-mix delivery quantities and short-load fees
- Verify the specified concrete strength and mix for the project
- Recheck access, placement method and total volume before ordering
How to use the result
Use the estimate to plan and compare options, then verify product-specific coverage, package size, density, installation requirements and local code before purchasing. BuildQuantify does not replace a supplier quote or professional design where one is required.
Frequently asked questions
Should I add extra material?
Usually yes. Cuts, breakage, uneven surfaces, compaction and measurement differences can increase real-world use. Choose a waste allowance that matches the job.
Can I use this estimate to place an order?
Use it as a planning estimate, then confirm package sizes, coverage, density and minimum order quantities with the manufacturer or supplier.