Rebar Calculator
Estimate rebar for a slab grid by spacing.
Enter your slab dimensions and the grid spacing to get the total linear feet of rebar and the number of bars running each direction. Use this for slabs, driveways, and footings reinforced with a rebar grid.
How it works
Bars run in two directions. The number of bars in each direction is the slab dimension divided by the spacing, plus one. Multiply each count by the length it spans, then add the two totals for the linear feet of rebar to buy.
Frequently asked questions
How much rebar do I need for a slab?
Count the bars in each direction (slab dimension ÷ spacing, plus one), multiply by the length each spans, and add them up. A 10×10 slab at 12-inch spacing needs about 220 linear feet.
What spacing should rebar be?
12 to 18 inches on center is common for residential slabs, but always follow your engineer or local code for structural work.
Does this include lap splices?
No — add extra length for overlaps where bars join, typically about 40 bar diameters per splice.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.