Rebar Calculator
Enter your slab dimensions and the spacing between rebar bars to find how many bars you need, their total length, and the number of intersections (for tying).
How a rebar grid is calculated
A rebar grid has bars running in two perpendicular directions. The number of bars running along the slab's length is based on how many fit across its width at the given spacing (and vice versa) — each full width or length needs one extra bar beyond the number of gaps, since bars sit at both edges.
Total rebar length adds up every bar's length in both directions. The number of tie intersections (where bars cross and need to be wired together) is simply the bars in one direction multiplied by the bars in the other.
Frequently asked questions
What's a typical rebar spacing for a slab?
This varies significantly by slab thickness, load requirements, and local building codes — common residential slab spacing is often 15-30 cm, but always follow your project's structural specifications.
Why do I need one more bar than the number of spacing gaps?
Bars are placed at both edges of the slab as well as at each interior spacing interval, so N gaps between bars always means N+1 bars total.
Does this calculator account for rebar overlap/splicing?
No — this gives the theoretical straight-bar length for a single grid layer. If your slab needs bars longer than standard rebar lengths, you'll need to add extra length for overlapping splices, which this calculator doesn't include.