How to Calculate Rebar for a Slab

Rebar for a slab is typically laid out in a grid — for example, bars every 18 inches in both directions. To estimate quantity, divide the slab's width by the spacing to find how many bars run one direction, then divide the length by the spacing for the other direction, and add one extra bar to each total (since a grid needs a bar at both edges, not just between them).

Rebar is sold in standard 20ft sticks, so the final step is converting total linear footage needed into a stick count, rounding up — partial sticks still mean buying a full one.

The Rebar Calculator does the full grid-to-stick-count conversion from your slab dimensions and spacing.