How it works
Bars run both directions on a grid. Count in each direction = (span ÷ spacing) + 1, then add up all the bar lengths.
Example
A 10 × 10 ft slab at 12 in spacing needs 11 bars each way — about 220 linear feet (11 × 20 ft bars).
Rebar Calculator
Work out how much rebar a slab needs — total linear feet and the number of bars to buy — for a grid at your chosen spacing.
- Free
- No sign-up
- Instant results
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Frequently asked questions
- What spacing should I use?
- 12–18 inches on centre is common for residential slabs. Check your local code and the slab's load.