How to Calculate Rebar
What is Rebar?
Rebar Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Rebar Spacing = 12 inches typical; Quantity = (Length / Spacing) + 1 per row
Step-by-Step Guide
- 1Determine grid spacing per code, calculate rows and columns
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
20 × 30 ft slab, 12-inch spacing both ways
Result
Rows: 21 × 20 ft bars + 31 × 30 ft bars = 52 bars
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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