Patio preset — 4 in slab · #4 @ 18 in OC typical
4 in thick, #4 @ 18 in OC.
6 in thick, #4 @ 12 in OC.
20×40 ft, 5 in, #4 @ 12 in.
40×30 ft, 8 in, #5 @ 12 in.
Volume math matches our concrete volume calculator. Reinforcement grid matches slab rebar calculator logic with effective cover.
No. It is a planning calculator for quantity and weight. Bar size, spacing, and thickness must meet approved drawings.
Bag count uses 80 lb yield by default for comparison. Most large slabs order ready-mix by the yard instead.
Concrete cost = cubic yards with waste × your $/yd entry. Steel cost is not included—add material quotes from your supplier.
This tool uses one spacing value both ways. Asymmetric grids need manual adjustment or engineering takeoff.