Rebar Calculator

What this rebar calculator covers

Slab reinforcement is usually discussed in terms of bar size and spacing, but ordering and pricing decisions often need a quantity-based estimate. A simple slab rebar calculator bridges that gap by converting a spacing layout into bar count, total linear length, and weight.

This page is meant for early planning on simple rectangular slabs. It assumes a two-way orthogonal grid, a consistent cover dimension around the slab edge, and one bar size throughout the layout. That makes it useful for takeoff and procurement checks, while still staying honest about what a true structural bar schedule requires.

Core slab rebar formulas

The calculation starts from the clear slab dimensions after cover is deducted. It then works out how many bars fit at the chosen spacing in each direction and multiplies those bar counts by the clear run lengths to estimate the total reinforcing steel length.

How to use the rebar quantity result

Use the bar count to sense-check the grid, the total linear length to compare supplier rates, and the weight to understand handling or delivery implications. If you enter a price per foot or metre, the calculator also gives a quick material-cost planning number for the same layout.

For example, a 20 ft by 12 ft slab with 1 ft spacing and 3 in cover works out to 12 bars in one direction and 20 in the other, with about 464 ft of total rebar in the grid. That gives you a fast starting point for procurement before the structural drawing is finalized into a detailed bar schedule.

What this result does not cover

This tool does not replace a structural bar schedule. It does not check code minimums, crack-control requirements, lap locations, chairs, splice types, hooks, development length, openings, thickened edges, or any reinforcement changes at beams, columns, or control joints.

Use it for early slab rebar planning only, then confirm the final bar size, spacing, cover, and detailing from the structural drawings and the applicable design requirements.