Use it for a planning range
- Enter slab length, width, thickness, and a waste allowance to calculate raw and order-ready cubic yards.
- Choose the non-structural slab use, finish, broad US region, reinforcement, base prep, old-slab removal, and placement access.
- Use bag counts for quantity checking, then compare bagged mix with ready-mix, short-load, delivery, standby, and pump requirements.
- Compare installed quotes by the same area, thickness, ordered yards, base depth, reinforcement, forms, finish, joints, curing, access, demolition, cleanup, and exclusions.
Example concrete slab estimate
- 24 ft by 20 ft slab
- 4 inch thickness
- 10% waste, broom finish, wire mesh, standard gravel base, direct truck access, no demolition, and US national baseline
The 480 sq ft slab uses about 5.93 raw cubic yards or 6.52 ordered cubic yards with waste: roughly 587 40-lb, 392 60-lb, or 294 80-lb bags. The reviewed model returns a $3,200–$8,140 installed planning range, with a $5,040 typical case and a separate $1,080–$1,940 ready-mix material-and-delivery allowance.
At this volume, ready-mix is normally the practical procurement baseline. Confirm truck reach, short-load fees, standby time, ordered-yard rounding, and whether a pump is needed before scheduling.
Small bagged-mix crossover example
- 10 ft by 10 ft slab
- 4 inch thickness with 10% waste
- Basic non-structural use with straightforward access
The order quantity is about 1.36 cubic yards: roughly 123 40-lb, 82 60-lb, or 62 80-lb bags. The calculator flags this as a crossover quantity where bag price and mixing labor should be compared with a ready-mix short-load fee.
Bag counts are quantity equivalents, not a recommendation to hand-mix. Consider batch consistency, working time, mixer capacity, crew size, weather, and finish timing.
Common cost drivers
- Slab dimensions and thickness determine concrete volume, but small jobs can still have minimum charges.
- Base prep, excavation, grading, gravel depth, and compaction can dominate difficult sites.
- Stamped, polished, reinforced, or thickened-edge slabs cost more than basic utility slabs.
- Truck access, pumping, demolition, drainage, permits, frost depth, and soil conditions can materially change the quote.