Structural Materials
Rebar Weight & Quantity Calculator
Estimate reinforcing bar quantities for a preliminary rectangular slab grid. Enter the reinforced length and width, bar diameter, spacing, layers, stock length, and steel price to review directional bar counts, grid length, purchase allowance, weight, and indicative cost.
Measurement System
Switch units without changing the underlying calculation.
Reinforcement grid
Exact rectangular grid
Models both bar directions from the reinforced length and width, then separates theoretical grid length from the purchase allowance for cuts and laps.
Input Dimensions
Calculation Results
Planning estimate only
Results are based on the values and assumptions entered here. Confirm quantities with current product information and suppliers; use qualified local professionals for structural, safety-critical, permitted, or code-regulated work.
Read the calculator terms and limits →Before you use the result
Professional estimating notes
Use the project drawings to confirm bar diameter, spacing, cover, lap lengths, hooks, and development details before ordering steel.
The rectangular grid model is intended for early estimating. Irregular slabs, beams, footings, openings, chairs, dowels, and congested reinforcement require a separate takeoff.
The 10% allowance is a planning assumption for cutting and laps, not a code requirement. Compare it with your bar schedule and supplier stock lengths.
Confirm whether your supplier quotes reinforcing steel by metric tonne, US ton, piece, or bundle, and use the matching display unit when pricing.
Questions answered
Rebar calculator questions
How does the rebar calculator estimate bar count?
It uses the actual reinforced length and width. It counts bars running in each direction from the selected spacing, includes an outside-edge bar, applies the selected number of layers, and then adds a 10% planning allowance for laps, cuts, and offcuts.
Why are the two directional bar counts different?
For a rectangular panel, bars that run along the length are spaced across the width, while bars that run along the width are spaced across the length. The counts are equal only when the reinforced panel is square.
Does this calculator design structural reinforcement?
No. It provides a preliminary quantity and weight estimate only. Bar size, grade, spacing, lap lengths, cover, anchorage, and detailing must come from the project design and applicable code.
Why is a 10% purchase allowance included?
Cutting, lap splices, hooks, and offcuts mean the theoretical grid length is not the same as the stock material required. Review the allowance against the bar schedule and available stock lengths with the reinforcing steel supplier or detailer.