Rebar Calculator
Lay out a rebar grid for a slab (bars in each direction, total linear feet, and grid intersections for tie wire) from the slab size, spacing, and edge clearance. Calculates in your browser.
Total rebar
-
Show the math
Bars in each direction fill the usable span after edge clearance:
bars = ⌊usable span ÷ spacing⌋ + 1
linear ft = Σ (bars × bar length)
Residential slabs often use #3 or #4 bar at 12–18 inches on centre each way. Each grid crossing is usually tied with wire. Follow your engineer or local code for structural work. All math runs locally in your browser.
What this does
A rebar calculator lays out a reinforcing grid for a slab (bars each way, total linear feet, and grid intersections for tie wire) from the size, spacing, and edge clearance.
How to use it
- Enter the slab length and width.
- Set the bar spacing.
- Set the edge clearance.
- Read the bars, linear feet, and ties.
How it works
Each direction divides the usable span by the spacing and adds one. Residential slabs often use #3 or #4 bar at 12–18 inches on centre.
bars = usable span ÷ spacing + 1
Understanding your result
This lays out the grid and counts bars and tie points, but it is a layout aid, not a structural design. Keeping the specified cover from edges and the ground is what protects the steel from rust, so do not skimp on clearance. For anything load-bearing, follow your local code and an engineers spec rather than a generic grid.
Example
A 10×10 ft slab at 12-inch spacing needs about 11 bars each way.
Sources & methodology
Last updated .
Frequently asked questions
What rebar spacing should I use?
Residential slabs commonly use #3 or #4 bar at 12–18 inches on centre each way. Follow your engineer or local code for structural work.
How is the bar count found?
The tool divides the usable width and length (after edge clearance) by the spacing and adds one, then sums the linear feet for both directions.
What are intersections for?
Each grid crossing is usually tied with wire; the intersection count helps you estimate ties and labour.
Do you store my numbers?
No. Everything is calculated locally in your browser.
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