Rebar Calculator
Bars, linear feet and 20 ft sticks for a two-way rebar grid in your slab.
Rebar grid calculator
You need
28 sticks
28 bars · 560 linear ft
Estimated cost $196 – $364
Back to the slab calculator
Laying out a rebar grid
A slab is reinforced with a grid of bar running both directions, tied where they cross and held up on chairs so the steel sits in the middle third of the slab. Closer spacing means more steel and better crack control.
Arrived from the slab calculator? Your slab size is pre-filled. Return to the slab calculator to size the concrete and base.
Prices updated January 2026 National US averages · reviewed quarterly
Volumes use standard bag yields and a 10% waste allowance; costs are national US averages that vary by region, mix and finish. See our methodology for exactly how each figure is worked out, or check the reference sources:
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Frequently asked questions
How much rebar do I need for a slab?
Lay a two-way grid at 12"–18" on-center. Bars = span ÷ spacing + 1 in each direction. This calculator adds both directions, totals the linear feet and rounds up to 20 ft sticks.
What spacing should rebar be in a slab?
18" on-center is common for residential slabs; tighten to 12" for driveways and heavier loads. Set your spacing above.
What size rebar for a 4-inch slab?
#3 (3/8") or #4 (1/2") bar is typical for a 4" residential slab. This calculator prices #4, the most common choice.