Understanding Rebar Sizes
Rebar (short for reinforcing bar) is sized by diameter. In the US, sizes are based on eighths of an inch. For example, #4 rebar is 4/8 inches, or 1/2 inch in diameter.
Common Sizes & Applications
- #3 (3/8"): Low stress applications like swimming pools and small sidewalks.
- #4 (1/2"): The most common size for residential driveways, patios, and slabs.
- #5 (5/8"): Used for heavier load-bearing foundations and commercial slabs.
Tips for Ordering
Rebar is typically sold in 20-foot lengths. Always tackle calculating total linear footage first, then divide by 20 to find out how many sticks you need. Add 5-10% extra for overlaps (splices) where two bars join together.
Frequently Asked Questions
What is the standard weight of #4 rebar?
#4 rebar (1/2 inch diameter) weighs 0.668 pounds per foot (lbs/ft) or 0.994 kilograms per meter (kg/m). A standard 20-foot bar weighs approximately 13.36 lbs.
How do I calculate rebar weight manually?
For imperial: Weight (lbs/ft) = (Diameter in inches)² × 2.67. Or simply Diameter (in inches)² / 0.375? No, the standard formula is roughly Volume × Density. A simpler rule: (Bar #)² / 9 gives approx weight in lbs/ft for sizes up to #9? No, calculating via volume is best. Or use charts.
What size rebar do I need for a driveway?
For a residential driveway, #3 (3/8") or #4 (1/2") rebar spaced 18-24 inches apart in a grid pattern is standard.
