What this site is
Steel Rebar Calculator (RebarCalc) is a collection of 21 free, browser-based calculators for reinforcement steel. There are no accounts and no sign-ups — open a calculator, enter your numbers, and get the answer. The tools cover five groups:
- Weight — bar weight per metre, per foot, and per tonne.
- Estimating — slab, footing, driveway, pool, wall, beam, column, and concrete-and-rebar takeoff.
- Members — reinforcement for beams, columns, and walls.
- Detailing — spacing, lap and development length, hooks and bends, stirrups, mats, and tie wire.
- Commercial — tonnage, quantity, and cost estimates for ordering.
Every calculator shows its formula and a worked example, so you can check the result by hand instead of trusting a black box.
Who it is for
Site engineers and foremen doing a quick takeoff, estimators pricing a job, students learning reinforcement detailing, and homeowners trying to understand what their slab or footing actually needs. The tools are written for all of them: the inputs are the same numbers that appear on a drawing — dimensions, spacing, cover, bar size.
How the calculations work
The core formula is the standard bar weight per metre, kg/m = d² ÷ 162.28, where d is the bar diameter in millimetres. Takeoff methods follow commonly used practice in IS 456, ACI 318, and ASTM A615 — for example, slab grids are counted in both directions after subtracting the edge cover from each side, and lap lengths are derived from development length. Where a result depends on a design decision — bar size, spacing, cover — the calculator asks you for it rather than guessing it.
What this site is not
These calculators are estimating and learning tools, not a substitute for a structural design. Results are estimates for guidance only: always verify them against your structural drawings and the design code that applies to your project, and have a qualified engineer check anything that carries load.
Free, and staying free
All 21 calculators are free to use, with no paywall and no account. The site is supported by advertising, which is why you will see a privacy policy and ad disclosures alongside the tools.
Contact
Found a mistake, or want a calculator we don't have yet? Tell us through the Contact page — corrections from working engineers are how these tools get better.