FORMULAS
Concrete & Rebar Quantity Calculator in Excel
10 min read · Template referenced below
Rather than calculating concrete volume and rebar quantities by hand for every slab or footing, a single Excel sheet with the right formulas can handle dozens of pours and instantly show totals for an entire project.
1
List your slab dimensions.
Create columns for Length (ft), Width (ft), and Thickness (in) — one row per slab or footing.
2
Calculate cubic yards.
=(Length*Width*(Thickness/12))/27 converts length × width × thickness in inches into cubic yards directly in one formula.
3
Estimate rebar length.
For a slab reinforced on a grid, rebar length ≈ (Length/Spacing+1)*Width + (Width/Spacing+1)*Length, where Spacing is your rebar spacing in feet (e.g. 1.5 for 18" on-center).
4
Convert rebar length to weight.
Multiply total rebar length by the unit weight for your bar size (for example, 0.376 lb/ft for a #4 bar) to get total pounds needed.
Prefer not to build the rebar weight formulas from scratch? BuildQuantify's
Rebar Weight Calculator does this instantly online — useful for spot-checking your spreadsheet's output.
Once built, this sheet becomes a fast way to compare pour sizes across a whole site plan and generate a single concrete order and rebar cut list in one pass.
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