Rebar Calculator
Enter your slab dimensions and grid spacing to estimate the number of rebar bars in each direction, the total linear feet, and the number of grid intersections to tie.
Results
- Total rebar length
- 269.5 ft
- Bars (lengthwise)
- 7 × 19.5 ft
- Bars (widthwise)
- 14 × 9.5 ft
- Tie intersections
- 98
Estimates only. Round up and buy a little extra to account for waste, spills, and breakage.
Enter your slab dimensions and grid spacing to estimate the number of rebar bars in each direction, the total linear feet, and the number of grid intersections to tie.
How to use the rebar calculator
- Enter the slab length in ft.
- Enter the slab width in ft.
- Enter the grid spacing in in.
- Enter the edge clearance in in.
- Optionally add a price to estimate the total project cost.
- Read your quantities instantly — no sign-up, and you can print the estimate to take to the supplier.
Worked example
Inputs
- Slab length
- 20 ft
- Slab width
- 10 ft
- Grid spacing
- 18 in
- Edge clearance
- 3 in
Results
- Total rebar length
- 269.5 ft
- Bars (lengthwise)
- 7 × 19.5 ft
- Bars (widthwise)
- 14 × 9.5 ft
- Tie intersections
- 98
Using the example values above, the rebar calculator returns 269.5 ft (total rebar length). Change any field to match your own project and the numbers update instantly.
Formula
Bars = (dimension ÷ spacing) + 1 in each direction. Total length = bars × run length. Intersections = bars across × bars down.
Frequently asked questions
- What spacing should rebar be in a slab?
- Residential slabs typically use #3 or #4 rebar on a 16–18 inch grid; driveways and heavier loads use 12 inch spacing.
- How much rebar do I need for a concrete slab?
- Lay a grid both directions: add 1 bar to (each dimension ÷ spacing), multiply by the run length, and sum both directions for total linear feet.
- How far should rebar be from the edge?
- Keep rebar about 3 inches from each edge and roughly centered in the slab thickness so concrete fully encases it.
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