Concrete Slab Rebar Calculator

Work out exactly how much reinforcement your slab needs. Enter the slab dimensions, bar spacing and edge cover, and the calculator returns the bar count in each direction, total bar length, tie-wire intersections and the total steel weight.

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How to use: Concrete Slab Rebar Calculator

Enter slab length and width.
Set the bar spacing (centre-to-centre) and edge cover.
Pick the bar size to get the bar count and total weight.

Formula

Bars one way = floor((dimension − 2 × cover) ÷ spacing) + 1, repeated for both directions. Total weight = total bar length × kg/m.

See the full rebar weight chart (kg/m & lb/ft) →

Concrete Slab Rebar Calculator — FAQ

How much rebar do I need for a concrete slab?

Divide each slab dimension (less cover) by the spacing, add one, and do this both ways. Multiply each row by the bar length and the bar's kg/m.

What spacing should slab rebar be?

Residential slabs commonly use 150–300 mm centres; always follow your structural design.