Rebar Calculator

A slab mat is a grid, and the number of bars in it falls out of the slab size, the spacing and how far the steel is held back from the edges. Enter those, pick a bar size and the length of bar you can buy, and this returns the count running each way, the total linear feet, the weight, and the number of stock bars to order once lap splices are counted. Runs longer than a stock bar are spliced at the lap you choose in bar diameters; runs shorter than one are cut several to a bar. It is a quantity takeoff, so the bar size, the spacing and the lap still have to come off the drawings.

Measured In
Feet for the slab and inches for the spacing and the cover, or metres and millimetres. The lengths, the areas and the weights in the answer all follow it.

Slab size, grid spacing and how far the steel is held back from the edge. The tool works out both directions, the splices and the bars to buy.

The centre to centre gap between parallel bars, in inches or in millimetres to match the unit above.
Leave blank for a square grid at the spacing above.
How far the steel stops short of each edge. Three inches is the usual figure for a slab on grade, and that is what a blank box uses.
Each bar is listed as its own market sells it. A #4 is 12.7 mm and a 12 mm bar is not a #4, so these are two product lines rather than one converted; pick the bar you are buying.
Each length is listed as its own market sells it, the foot lengths and the metre lengths together, so pick the bar you can actually get rather than converting one into the other.
Quoted in bar diameters, which is a ratio and so the same number in either system.
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