Rebar Bar Size Guide: Choosing 3, 4, 5, or 6
Steel rebar is sized using a standard US numbering system where the bar number represents its nominal diameter in eighths of an inch. For example, a #4 bar equals 4/8 of an inch, or exactly 0.5 inches in diameter.
Selecting the correct rebar size is essential for ensuring your concrete project meets engineering load requirements without overspending on excess steel.
Calculate steel weight across all rebar sizes. Get exact linear foot and stick counts instantly.
Open Rebar Calculator
Open Rebar Calculator
Common Rebar Sizes and Their Applications
- #3 Rebar (3/8" / 0.375 in): Weighs 0.376 lbs/ft. Best for light residential sidewalks, driveways, wire mesh reinforcement, and garden walls.
- #4 Rebar (1/2" / 0.500 in): Weighs 0.668 lbs/ft. The standard choice for patio slabs, garage floors, swimming pool walls, and residential driveways.
- #5 Rebar (5/8" / 0.625 in): Weighs 1.043 lbs/ft. Used for load-bearing footings, retaining walls, and commercial slabs.
- #6 Rebar (3/4" / 0.750 in): Weighs 1.502 lbs/ft. Designed for heavy foundations, structural columns, and highway bridge decks.
Choosing Between #3 and #4 Rebar for Home Slabs
While #3 rebar works well for basic sidewalks, upgrade to #4 rebar spaced on 12-inch centers for any slab supporting vehicular traffic, such as a driveway or vehicle parking pad.
Calculate your steel grid weight with our free Rebar Calculator.
