About Concrete Calculator

Concrete Calculator exists to answer one deceptively hard question: how much concrete do I need? Between unit conversions, odd shapes, bag yields, waste allowances and regional pricing, a "simple" slab estimate has a dozen places to go wrong — and going wrong mid-pour is expensive.

Our site offers 52+ purpose-built calculators covering every common concrete project: slabs, footings, post holes, sonotubes, columns, walls, stairs, trenches, curbs and more — plus bag calculators for every size from 20 kg to 90 lb, mix ratio and grade tools, and specialty engineering calculators for rebar layout, slab load capacity, control joints and embodied carbon.

How our math is sourced

Every calculator uses the exact geometric formula for its shape and published constants for material behavior: manufacturer bag yields, standard concrete densities (2,400 kg/m³ normal weight), the 1.54 dry-volume factor for mix batching, ACI-referenced methods for joints, evaporation and slab loading, and ASTM bar data for rebar. Where a tool involves engineering judgment — load capacity, reinforcement — we state our assumptions on the page and tell you plainly to verify structural work with a licensed engineer.

Free, fast and private

Everything on this site is free, works on any device, and computes in your browser — your dimensions and project details are never sent to a server. No sign-ups, no downloads, no paywalls.

Get in touch

Found an error, want a calculator we don't have, or have a question about an estimate? Contact us — corrections and suggestions genuinely shape the roadmap.