Free Rebar Calculator Widget
The embedded Rebar Calculator converts a rectangular slab's dimensions, bar size and spacing into a two-way rebar grid — total bars, linear feet, weight and stock bars to buy. It suits rebar and building-material suppliers, and concrete contractor sites.
It's a single iframe plus a one-line credit link — free, responsive, no registration, and no ads or tracking scripts on your page.
Live preview
The embed adds no ads and no tracking to your page. Prefer a guided version with a preview? Use the embed builder.
Credit line included
The code ends with a one-line credit under the calculator: “Rebar Calculator by Build Material Planner”, linking to the full calculator. Please keep it. It's what keeps these calculators free to build and maintain, and it helps other people find them.
Why add it to your page
Rebar is sold in 20 ft stock bars, but a slab grid is laid out in runs as long as the slab, so counting grid bars isn't the same as knowing what to buy. The calculator gets from one to the other, which is what a reader needs at the supply counter.
What your visitors get
A 24 x 20 ft slab with #4 bar comes back as:
- Rebar #4 (1/2 in): 33 stock bars (20 ft)
- Rebar materials estimate: $231 – $363
Where the Rebar Calculator widget fits
- A rebar or building-material supplier's ordering page
- A "how much rebar do I need" article
- A concrete contractor's slab project-planning page
How to add it to your site
Copy the code above and paste it where the calculator should appear. See the install notes for WordPress, Squarespace, Wix and Webflow, plus sizing and common questions.
Questions from site owners
Does it support different bar sizes and spacing?
Yes — #3 through #6 rebar, with adjustable spacing and edge clearance.
Does it give weight, not just bar count?
Yes — total weight in pounds is calculated from the bar size's standard weight per foot, useful for ordering by weight.
What spacing does it start with?
18 in on center with 3 in of edge clearance. Readers can change both to match their plans.
Just need to run the numbers yourself? Use the full Rebar Calculator — it has the formulas, a worked example and an FAQ. Also for your readers: Concrete Slab Calculator widget, Gravel Driveway Calculator widget. Or see all embeddable calculators.