Rebar Calculator

The calculator does not select reinforcement spacing. Slab thickness, soil, loads, joints, exposure, and the adopted code or engineered plans control the layout. Use the plans or have a qualified concrete professional or engineer specify bar size, spacing, cover, laps, and supports.

The calculator lists #3 through #6 so you can estimate quantity and weight after the design is specified. Rebar size is not a general-use choice: it depends on loads, slab or footing geometry, soil, exposure, and the approved design. Do not choose reinforcement from a rule of thumb.

For each axis, subtract twice the edge offset from the slab dimension, divide by grid spacing, take floor, and add one. For a 240 in slab with 3 in offset and 12 in grid, that is floor((240 - 6) / 12) + 1 = 20 bars.

The 10% value is an editable purchasing allowance for a simple rectangular layout. It does not calculate development length, laps, hooks, bends, or a reinforcing schedule. Use approved plans to determine those details before ordering.

It is the number of grid intersections, which equals bars-lengthwise times bars-widthwise. Tie-wire coverage varies by wire type, tie method, and job conditions. Use the supplier's coverage information and the approved reinforcing detail when ordering.