Landscape & Groundwork
Rebar Calculator
Count reinforcing bars on a rectangular grid and estimate total length and straight stock.
Enter your measurements
Results update as you type.
About this calculator
Enter the slab rectangle, edge cover and the bar spacing you have been given in each direction. The calculator counts bars, totals their length and, when you enter a straight stock length, estimates how many pieces to buy without reusing offcuts across directions. It is one straight orthogonal layer — not a structural design.
How to measure
- Measure the rectangular length and width and enter the edge cover from the approved project plan.
- Enter spacing in both directions from that plan; the calculator does not design reinforcement.
- Stock length must accommodate each required straight cut. Separate direction groups do not reuse offcuts.
How to use this calculator
- Measure the slab rectangle and the clear edge cover.
- Enter the bar spacing supplied in each direction.
- Optionally enter the straight stock length you are buying.
- Calculate for bar counts, total length and stock pieces.
Formula
Effective length = length − 2 × cover; effective width = width − 2 × cover
Bars parallel to length = ⌈effective width ÷ spacing in that direction⌉ + 1
Bars parallel to width = ⌈effective length ÷ spacing in that direction⌉ + 1
Total length = bars × their cut length, summed for both directions
Stock pieces = ⌈bars ÷ floor(stock ÷ cut length)⌉ for each direction, then summed
Assumptions
- One straight orthogonal layer; bars run parallel to the rectangle sides.
- Spacing and cover are your inputs, not code recommendations.
- Stock pieces are counted per direction with no offcut reuse between directions.
Common mistakes
- Choosing bar spacing from the quantity calculator rather than the design.
- Ignoring cover, lap, hooks and cutting constraints.
- Treating a rectangular grid count as a detailed reinforcement schedule.
Worked example
Try it: press “Load example” above the form.
A 6 × 4 m grid at 2 m spacing needs 3 bars one way and 4 the other: 34 m total, and 7 pieces of 6 m stock.
Limitations
No bar diameter, lap, hook, structural strength or code design. Drawing is capped independently of the bar count.
Frequently asked questions
Does this choose bar size and spacing?
No. Obtain bar size, spacing and cover from the project design. Enter the specified spacing and cover here to count a simple grid and straight stock pieces; there is no bar-size design input.
Are lap splices and bends included?
No. This model excludes laps, hooks, bends, chairs and splice or anchorage allowances. Use the project bar schedule to calculate those separately; the straight-stock count is not a fabrication schedule.
What does the worked example show?
A 6 × 4 m grid at 2 m spacing needs 3 bars one way and 4 the other: 34 m total, and 7 pieces of 6 m stock.
Which assumptions should I check before using the result?
No bar diameter, lap, hook, structural strength or code design. Drawing is capped independently of the bar count.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
- Omni: rebar quantity calculator
Grid quantity context; the straight-stock grouping here excludes offcut reuse and structural design.
Calculation documentation · Updated 2026-11-11 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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