Free tool

Rebar spacing & quantity estimator

Enter the slab footprint and the bar spacing you are detailing to, and this returns the number of bars in each direction, the total linear feet of steel and how many stock bars that works out to.

Slab length (ft)

Slab width (ft)

Bar spacing (in o.c.)

Edge clearance (in)Concrete cover from the slab edge to the first bar.

Stock bar length (ft)

Rebar grid

Total linear

190

feet of bar

Stock bars

× 20 ft sticks

Bars lengthwise

running the length

Bars crosswise

running the width

Planning estimate. This is a plain grid count and does not include lap splices, bends, chairs or extra bars at openings and edges — add for laps (commonly 40 bar diameters). Reinforcement for structural work must follow your engineer's drawings and local code.

How the grid is counted

Bars run in both directions at a fixed centre-to-centre spacing, held back from every edge by the concrete cover you specify. The count in one direction is floor(usable span ÷ spacing) + 1 — the +1 is the bar at the far end, which is the step people most often miss.

Twelve inches on centre is the common default for a domestic slab; heavier slabs go to eight or six. The edge clearance is your cover — typically three inches where concrete is cast against ground.

This is a plain grid count. It does not add lap splices (commonly 40 bar diameters), bends, chairs, or the extra bars a detail calls for at openings, edges and corners — add those from your drawings. Need the concrete volume too? Use the slab calculator.