Rebar Calculator
Calculate the number of rebars and total length needed for a concrete slab.
Supports imperial and metric units.
Rebar Estimate
Rebar layout for a concrete slab is calculated based on slab dimensions and bar spacing.
Imperial (feet and inches):
Bars along length = floor(Width / Spacing) + 1
Bars along width = floor(Length / Spacing) + 1
Total bars = Bars along length + Bars along width
Total rebar length = (Bars along length × Length) + (Bars along width × Width)
Metric (meters and centimeters): Same formulas apply with metric measurements.
Common rebar spacing:
- 12 inches (30 cm) — Standard residential slabs
- 8 inches (20 cm) — Driveways and garage slabs
- 6 inches (15 cm) — Heavy-duty or structural slabs
Rebar sizes:
- #3 (10mm): 3/8 inch diameter — light residential
- #4 (12mm): 1/2 inch diameter — standard residential
- #5 (16mm): 5/8 inch diameter — driveways, structural
Tips: Always add 10–15% extra for overlaps and waste. Rebar should be placed at mid-depth of the slab or per engineering specs.