Rebar grid, sticks, tie wire & cost for slabs and footings
Enter your slab dimensions, grid spacing, and rebar size. The calculator lays out the grid — bars spaced on center with an edge clearance on each side — counts the bars running each direction, totals the linear footage (with lap for splices), converts to 20 ft sticks, estimates tie wire from the number of tied intersections, and prices the package by weight.
A 20 ft × 20 ft slab with #4 bar at 24 in on center, 3 in edge clearance: usable run = 20 − 0.5 = 19.5 ft → floor(19.5 ÷ 2) + 1 = 10 bars each way (20 total). Length = 10 × 20 × 2 = 400 ft + laps ≈ 420 ft = 21 twenty-foot sticks of #4, weighing ~280 lb. Tying every other intersection: ~50 ties ≈ 1 lb of wire. At $0.85/lb, steel costs about $240.
What size rebar for a 4-inch slab? #3 or #4 at 18–24 in on center is typical for patios and driveways. Wire mesh is an alternative for light-duty slabs, but rebar holds alignment better during the pour.
How much should rebar overlap? Lap splices are typically 30–40× the bar diameter (e.g., ~20 in for #4), or as specified by your engineer. Our default 2 ft lap per stick covers most cases.
How much tie wire do I need? Tying every other intersection with a figure-8 tie uses roughly 2 lb of 16-gauge wire per 1,000 linear ft of rebar; double it for every-intersection tying.
Does rebar pricing work by weight? Yes — rebar is sold by the pound or by the stick, but weight-based pricing is standard for orders over a few hundred pounds.