How to estimate rebar for a simple member

A bar bending schedule is prepared from the structural drawings. A quantity estimator is the step before that: enough to see the order of magnitude of steel in a slab, beam or column.

Bars across a span

The count is floor((span − 2 × cover) / spacing) + 1. The span and the spacing must use the same units. Spacing is centre to centre. Bars start at the near cover. If the clear distance does not divide exactly by the spacing, there is a shortfall before the far cover. The first and last bars do not both sit on the cover unless that distance divides exactly.

What the weight leaves out

The straight bar length used for a first estimate is the span minus cover at each end. Hooks, cranks and laps are extra and have to be added from the drawing. A rectangular tie is estimated as twice the inner width plus twice the inner depth, plus 24 tie-diameters for two hooks. Weight uses 7850 kg/m³. A wastage percentage is an ordering allowance, not a substitute for the schedule.