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Concrete Calculator

Estimate how much concrete you need for a slab, in cubic yards and 80 lb bags.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-25 · v1.0.0

Market
Imperial · sales tax
10 ft10 ft4 in
Schematic, drawn to the proportions you entered — not to scale on screen.
Who is doing the work?

The standard allowance most suppliers and estimating guides assume for ordinary work.

Estimated concrete needed

1.358 cubic yards

High confidence
Volume (no waste)
1.23 yd³
Volume with waste factor
1.36 yd³
Cubic feet
36.67 ft³
80 lb bags needed
62 bags

Code thresholds this tool can check — United States

Each check below names the body that published the limit it uses. Switching market re-runs them. This is not a code review and has no official standing.

These checks cover only the specific numeric limits listed below. They are not a complete code review: fire separation, egress, structural capacity and accessibility provisions are outside their scope, and only the handful of local amendments offered in the selector are modelled — your municipality may have others. Passing every check here does not make a design compliant. Final approval rests with your local building authority.

  • WITHIN LIMIT — Concrete floor slabs on ground: minimum 3.5 in (89 mm) thick.

    Slab thickness 4.00 in meets the 3.5 in IRC floor-slab minimum. Expansive soils are handled separately under IRC R403.1.8, and any slab carrying vehicles or point loads should be designed rather than taken from the code minimum.

    ICC · IRC R506.1

For the dimensions entered, expect a result of 1.36 cubic yards. Set for United States. The market selector changes the units and the trade terminology; any standard behind the formula is cited under sources.

Estimated cost

$190 - $238

  • Ready-mix concrete, delivered$190 - $238

Estimated national-average pricing, adjusted by a rough regional multiplier — not a quote and not verified for your specific location or supplier. Last verified 2026-08-25.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • Standard formula: cubic yards = length (ft) x width (ft) x thickness (ft) / 27
  • An 80 lb bag of pre-mixed concrete yields approximately 0.6 cubic feet once mixed

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Still deciding? Concrete Slab vs Pavers — the factors that actually differ, with no invented prices.

Frequently asked questions

Should I order exactly this amount from a ready-mix truck?
Order slightly more if you're unsure — ready-mix trucks usually charge a short-load fee for small orders anyway, and running short mid-pour is far worse than having a little extra.
How thick should my slab be?
4 inches (~0.1 m) is standard for patios, walkways, and shed floors. 6 inches (~0.15 m) is common for driveways carrying vehicle weight. Check local code for structural slabs.
Does this calculator account for rebar or wire mesh?
No — this estimates concrete volume only. Reinforcement is a separate material and structural decision, especially for driveways and load-bearing slabs.
Why 80 lb bags specifically?
80 lb bags are the most common size sold at hardware stores for DIY pours. If your bags are a different size, scale the bag count by the ratio of volumes.