20 ft x 12 ft grid at 18 in spacing
- Lengthwise bars
- 9
- Widthwise bars
- 14
- Adjusted linear feet
- 382.8 ft
This is a simple material takeoff. Structural spacing, bar size, laps, chairs, cover, edge distance, and local code need professional design.
Rebar Calculator
Use this free rebar calculator to estimate a simple two-direction rebar grid from slab dimensions, bar spacing, stock bar length, and waste.
Research-backed assumptions Formula steps Examples included Private in-browser use
Formula steps
- Count bars running each direction from the slab dimension and spacing.
- Multiply bar counts by the length each direction runs.
- Add waste, divide by stock bar length, and round up.
How to use the rebar calculator
- Enter slab length, slab width, bar spacing, stock bar length, and waste percent.
- Press Estimate rebar to see bars in each direction, adjusted linear feet, and stock bars to buy.
- Use this as a material takeoff only, not a structural design.
- Bar size, lap length, cover, supports, edge distance, and local code need professional review.
Common uses
Estimate stock rebar bars for a simple rectangular slab grid.
Compare 12-inch, 18-inch, and 24-inch spacing.
Add waste for cuts and lap planning.
Plan a rough material list before professional review.
Examples
20 bars
Rebar grid estimate
Linear feet and bar count
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Rebar Calculator?
Use it when your task matches one of these common needs: Estimate stock rebar bars for a simple rectangular slab grid. Compare 12-inch, 18-inch, and 24-inch spacing. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Rebar Calculator doing with my inputs?
In plain language: The calculator counts bars in both slab directions from spacing, totals linear feet, adds waste, divides by stock bar length, and rounds up. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What do the main Rebar Calculator inputs mean?
Slab length and width: the rectangular slab dimensions for the grid estimate. Bar spacing: the distance between parallel bars; smaller spacing means more bars. Stock bar length: the length of one purchased bar from the supplier. Waste percent: extra length for cuts, lap planning, and small layout changes.
How should I read the Rebar Calculator answer?
Read the headline estimate first, then check the material, waste, coverage, and unit lines. For project tools, the supporting lines are often the difference between a rough idea and a list you can actually shop from.
What should I double-check before trusting the answer?
This is a material takeoff, not structural design. Bar size, spacing, laps, cover, supports, edge distance, and code requirements need professional review. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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