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Rebar Calculator

Estimate the linear feet and number of rebar sticks needed for a rectangular grid inside a concrete slab.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.1.0

Market
Imperial · sales tax
13.12 ft9.84 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Estimated rebar needed

11 x 20 ft sticks

Check your inputs

General-purpose slab reinforcement guideline, not a structural engineering design — load-bearing or code-required slabs should follow an engineer's specification.

Total linear feet (incl. 15% lap splice)
207.51 ft
Bars running lengthwise
7 bars
Bars running widthwise
9 bars

For the dimensions entered, expect a result of 11 x 20 ft sticks. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Add the equipment this sizes

This result is a specification — 11 x 20 ft sticks — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Rebar is most commonly sold in 20 ft lengths; grid spacing for residential slabs is commonly 12-18 in on-center in both directions
  • A 15% lap-splice allowance is added to account for the overlap required where rebar sticks join end-to-end across a run longer than one stock length, per common ACI 318 lap-length practice

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Frequently asked questions

Is this a structural engineering calculation?
No — this is a general material-quantity guideline for common residential slab reinforcement patterns. Load-bearing slabs, foundations, and anything requiring a permit should follow a structural engineer's rebar specification.
What rebar size (diameter) should I use?
This calculator estimates linear footage and sticks regardless of bar diameter (commonly #3 or #4 for residential slabs) — diameter affects strength, not the grid layout calculated here.
Do I need rebar for every concrete slab?
Not always — thin non-structural slabs (some sidewalks) sometimes use wire mesh instead, or no reinforcement. Check local code requirements for your specific project.