Rebar Calculator
Updated Formulas shown
A 20 × 20 ft slab with rebar 16 in on center each way needs about 31 pieces of 20 ft bar including 12 in laps.
Rebar pieces
31
20 ft bars incl. 12 in laps
- Total length
- 585 ft
- Bars along length
- 15
- Bars along width
- 15
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Frequently asked questions
What rebar spacing for a 4 inch slab?
#3 or #4 rebar at 12–18 in on center each way is typical for residential slabs; driveways usually 12 in.
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Estimates only. Check quantities with your supplier or contractor before ordering.