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Concrete calculator.
Slabs, footings and walls.

Multiply length × width × height in matching units to estimate concrete volume. Divide cubic feet by 27 for cubic yards, then add your chosen waste allowance. Calculate below or follow the worked examples.

Choose the unit beside each dimension. Switching units converts your measurements; it does not clear them.

Dimensions

Allow for the pour

Default 5%. Adjust from 0% to 20% for your job.

Your estimate

Enter dimensions and select Calculate concrete.

Plan the quantity. Check the order.

This is a geometric quantity estimate, not a structural design or a supplier order. Confirm field dimensions and ordering requirements before the pour. Results use full calculation precision and round only for display.

Measurements stay in this browser session. No account, payment, or upload is needed.

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FIELD GUIDE

How do I calculate concrete for a slab, footing or wall?

For a rectangular section, multiply length × width × thickness or height in the same units. Divide cubic feet by 27 to get cubic yards. Add your chosen waste allowance after calculating the base volume. Sooport reports cubic yards, cubic metres and cubic feet.

  1. Open the concrete calculator and select the rectangular shape for slabs, strip footings or straight walls.
  2. Select US customary or metric units. Use each input’s unit selector: 4 inches is not 4 feet; 100 mm is 0.1 m.
  3. Enter length, width and height/thickness, plus the number of identical sections. For a wall, width is wall thickness and height is wall height.
  4. Set the waste allowance (0–20%; default 5%). Subtract a rectangular void only if it fits within the section. Calculate different sections separately and avoid counting overlapping corners twice.
  5. Review base and adjusted volume. If using truck estimates, enter the supplier’s load capacity; the tool rounds the load count up to a whole truck.

Worked examples

  • Slab: 20 ft × 12 ft × 4 in = 20 × 12 × (4 ÷ 12) = 80 ft³ = 2.963 yd³. With 5% extra: 3.111 yd³. Use the slab calculator.
  • Footing: 40 ft long × 24 in wide × 12 in deep = 80 ft³ = 2.963 yd³; with 5%: 3.111 yd³. Use the footing calculator.
  • Wall: 30 ft long × 8 in thick × 8 ft high = 160 ft³ = 5.926 yd³; with 5%: 6.222 yd³. Use the wall calculator.
  • Metric slab: 6 m × 4 m × 100 mm = 2.4 m³; with 5%: 2.52 m³.

Before ordering concrete

The 5% default is a calculator setting, not a recommendation for every pour. Check formed dimensions, excavation variation, placement losses and delivery increments with your supplier. Rounded results are estimates, not a purchase order. The tool does not specify strength, reinforcement, mix design or structural adequacy. Separate hollow walls, complex intersections and irregular excavation into measurable sections.

Common questions

Does the tool handle shapes other than rectangles?

Yes. It includes round columns and holes, circular slabs and tubes, curb sections, and solid stairs. Choose the matching mode and check the diagram before entering dimensions.

Does the waste percentage change my base volume?

No. The base is geometric volume. Total volume is base × (1 + waste percentage ÷ 100); quantity repeats the complete section.

Can I use the calculator without an account?

Yes. Calculations run in your browser. JavaScript is needed for interactive results, but the formulas and examples on this page are readable without it.

Primary reference

For ordering considerations beyond volume, see NRMCA Concrete in Practice, CIP 31: Ordering Ready Mixed Concrete. Confirm the project specification and order with your concrete supplier.

Published by Sooport, founded by construction superintendent Jonathan “Jono” Boyce. Guidance reviewed against the site’s tools and linked references on .