Concrete Slab Cost Calculator

A 400-sq-ft pad at the standard spec — 4 in. thick, broom finish, wire mesh, minor grading over a gravel base — runs about $3,168 nationally, with most pours landing between $2,534 and $4,277. The same slab with a stamped finish moves to roughly $4,751 ($3,800–$6,413).

One cubic yard covers about 81 sq ft at 4 in. A 20 × 20 ft slab works out to ≈4.9 yd before waste; order 5.5 yd to cover spillage and an uneven subgrade, in half-yard steps. Suppliers charge minimums on small loads — expect a fee any time the order is under a full ~10-yd truck.

Rarely. An 80-lb bag yields 0.60 cu ft, so one cubic yard takes about 45 bags — roughly $270–$405 per yard at $6–$9 retail, versus $119–$147/yd delivered. Bags only win for patches and footings under about a yard, or where a truck (and even a line pump) physically cannot reach.

Backyard patios and shed pads usually fall outside permit requirements, but driveway aprons, curb cuts, anything crossing a utility easement, and slabs over a certain size often need a zoning or right-of-way permit — and some HOAs want an approval letter either way. One step is required no matter what you pour: call 811 a few business days ahead for the free utility locate, because excavation and post-hole work is exactly where buried gas and electric lines get struck. Ask your building department before scheduling the truck; pour day is the wrong day to find out.

Walkways, patios and shed pads are fine at 4 in. Cars need at least 5 in., and trucks, RVs or a hot tub call for 6 in. over a rebar grid — the minimums Estimators.us publishes for 2026. Thickness is the cheapest strength you can buy: each extra inch adds ~25% more yardage but only a few hundred dollars on a 400-sq-ft pour.

Foot traffic in 24–48 hours, furniture and grills after about a week, vehicles at the 7-day mark once the mix reaches roughly two-thirds strength, and full design strength at 28 days. Keep it damp during hot, dry curing weather — the difference between curing and drying is the difference between a hard slab and a dusty one. Hold sealers until the full cure is done, though: sealing early traps bleed water in the slab and clouds the finish.

A ready-mix chute reaches only a few feet past the truck, so anything behind the house or across soft ground needs a line pump ($15/yd with a $125 minimum, plus setup) or a boom pump ($140–$190/hr with 4–5 hr minimums). On a typical 5.5-yd backyard pour a line pump adds a few hundred dollars — usually less than the wheelbarrow crew it replaces.

Concrete shrinks as it cures, and shrinkage cracking is inevitable unless the slab is scored so it cracks where you choose. Control joints should be saw-cut within 24 hours and spaced about 8–12 ft apart on a 4-in. slab. Joints do not fix a soft or uncompacted base — settlement cracks follow the base, not the grid.