Concrete calculator
About Concrete calculator
This concrete calculator helps homeowners, contractors, and estimators turn simple dimensions into order-of-magnitude yardage before calling a ready-mix plant or buying bags. It covers rectangular slabs and walls (length × width × thickness), round columns or piers (cylindrical volume), hollow circular sections (outer minus inner, with inner diameter set to zero for a solid disk), a transparent mono-slab model for stairs, and a two-part strip model for curb and gutter lines. You choose the measurement unit, optional waste percentage for spillage and uneven pours, and a concrete density in pounds per cubic foot so the page can show approximate weight in pounds and kilograms. Nothing is uploaded: all arithmetic runs locally in your browser, consistent with other AllOneTools calculators.
Key Features
- Slab / pad / wall: rectangular volume with quantity multiplier
- Round column / pier: cylinder from diameter and height
- Hollow round (tube): annular volume; inner diameter 0 yields a solid round volume
- Stairs: mono-slab planning model using run, rise, width, platform, and thickness
- Curb line: strip cross-section × run length (documented simplification)
- Outputs cubic yards, cubic feet, cubic meters, approximate weight, and bag counts
- Waste percentage and editable density for different mixes
Use Cases
- Order-of-magnitude check before a ready-mix quote or delivery minimum
- Back-of-truck estimates for sonotubes, sidewalk strips, and small pads
- Teaching volume geometry with a practical construction context
Pro Tips
- Ready-mix is often sold by the cubic yard in the US; rounding up one quarter yard beats a short load on site.
- Bag yields vary by product line—treat bag counts as illustrative unless you match the manufacturer sheet.
- For structural elements, thickness and rebar cover belong in engineered drawings, not a generic web form.
Frequently Asked Questions
Is this concrete calculator the same as an engineered takeoff?
No. It applies basic solid geometry to numbers you supply. It does not model mesh, chairs, voids, haunches, or code-minimum cover. Use it for planning and education; rely on stamped drawings and qualified professionals for structural work.
Why can I change density?
Normal-weight ready-mix is often approximated around 145–150 lb/ft³ for estimating weight on trucks and subgrade loading. Lightweight or high-density mixes differ; adjust the field if you know your supplier mix class.
How accurate are bag counts?
They divide total cubic feet (after waste) by rough per-bag cured yields (~0.60 ft³ for an 80 lb bag and ~0.45 ft³ for a 60 lb bag). Real yields depend on admixtures, voids, and how you place the mix—always follow the bag label for your SKU.
Does AllOneTools store my measurements?
No. The tool runs entirely in your browser with no server round-trip for your dimensions, matching the privacy model of our developer and SaaS calculators.