Rebar Calculator
Estimate rebar length, steel weight, bar count and project cost for slab, column, beam, footing & wall reinforcement — with engineering drawings and a printable PDF report.
Material cost estimate (optional)
How to estimate rebar
Three simple steps to a complete steel reinforcement estimate.
Slab, column, beam, footing, wall or custom layout — choose the element so the right reinforcement layout is calculated.
Add dimensions, bar diameter, spacing, hook and lap lengths, and concrete cover. Metric and imperial both work.
Total rebar length, steel weight in kg and lb, number of main bars, stirrups, and optional cost — clearly broken down.
Rebar Calculator — Free & Accurate
Our rebar calculator helps structural engineers, site supervisors, estimators, and DIY builders estimate the steel reinforcement needed for any concrete element. Pick a layout — slab, column, beam, footing, wall, or custom — enter the dimensions, bar diameter, spacing, and concrete cover, and get a complete steel schedule in seconds.
The calculator uses the industry-standard formula kg/m = d² ÷ 162.16 (where d is the bar diameter in mm) to convert total rebar length into weight. Steel density is taken at 7,850 kg/m³. For slabs, footings, and walls, the calculator computes a two-way mesh: bars in both X and Y directions at your chosen spacing, with hooks and laps added per bar. For columns and beams, you get both main longitudinal bars and stirrups (closed loops at spacing). Concrete cover is deducted from each face to give the true rebar length.
Results show total rebar length (m and ft), steel weight (kg and lb), number of main bars, stirrup count, bar diameter and unit weight, and wastage allowance — plus an optional cost estimate including steel and labor in your local currency. Everything runs in your browser — no signup, no data sent to any server.
Why use this calculator?
Built for the site, not the spec sheet — simple, fast, and accurate.
No spreadsheets, no formulas to memorise. Type your sizes, hit calculate, and you're done.
Uses the kg/m = d² ÷ 162.16 formula, deducts cover, and handles hooks, laps and two-way meshes automatically.
Everything runs in your browser. Your dimensions never leave your device.
Mix metres, feet, inches, and centimetres on the same job — the math converts cleanly.
Tells you total steel weight, rebar length and bar count — exactly what your supplier and bar-bender need to quote.
Open it on your phone right at the workshop. Fully responsive, no app needed.
Related construction tools
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Frequently asked questions
The industry-standard formula is kg/m = d² ÷ 162.16, where d is the bar diameter in mm. This comes from steel's density (~7,850 kg/m³) and the circular cross-section area (π·d²/4). For example, a 12 mm bar weighs 12² ÷ 162.16 ≈ 0.888 kg per metre, a 16 mm bar ≈ 1.578 kg/m, and a 20 mm bar ≈ 2.466 kg/m. Multiply the total length (in metres) by the kg/m value to get the total weight.
For a two-way slab mesh: bars in the long direction = ((W − 2·cover) ÷ spacing) + 1, each of length L + 2·hook. Bars in the short direction = ((L − 2·cover) ÷ spacing) + 1, each of length W + 2·hook. Total length = (count_long × length_each) + (count_short × length_each). For bars longer than the standard stock length (12 m), lap splices add ~40–50× the bar diameter at each splice. The calculator factors all of this in automatically.
Concrete cover (the distance from the rebar to the outer concrete face) depends on exposure. Typical values: slabs and walls indoors 20–25 mm; beams and columns 25–40 mm; footings and members in contact with soil 50–75 mm. Marine or aggressive environments need 50+ mm. The calculator subtracts twice the cover from each dimension to give the true working length of the rebar inside the concrete.
A hook is a bent end (usually 90° or 135°) added to anchor the bar into the concrete. Typical hook length is 9× to 12× the bar diameter — about 75–150 mm for common sizes. A lap is the overlap between two bars joined end-to-end so they act as one continuous bar; typical lap is 40× to 50× the bar diameter (e.g. ~500 mm for a 12 mm bar). Both are added to your computed rebar length so the order is correct.
Yes. Every dimension has its own unit picker, so you can enter the slab length in feet, the bar spacing in inches, and the cover in mm on the same calculation. The math converts everything to consistent units internally. Steel weight is reported in both kg and lb so it matches your supplier's quote.