Rebar Calculator

How to estimate rebar for a slab

1. Enter the slab length and width, the bar spacing and the edge cover.
2. Choose the bar size and the length of stock bars.
3. See the number of bars each way, the total length and the weight.

Frequently asked questions

Does it include laps?

No. Where bars have to be joined, add the lap length your design calls for, often 40 to 60 bar diameters.

How is the number of bars worked out?

The width to cover, less the cover at both edges, divided by the spacing, rounded down, plus one.

How much cover does rebar need?

It depends on the exposure. Indoor slabs often need about 20 to 25 mm, and concrete cast against the ground about 75 mm (3 in).