#4 Rebar Weight Per Foot (Chart + Calculator)

Determining the weight of #4 reinforcing steel rebar (1/2-inch nominal diameter) is a critical step in structural concrete calculations. Reinforcing bars are manufactured with surface deformations (ribs) to bond mechanically with concrete. Under ASTM A615 guidelines, a #4 bar has a nominal weight of 0.668 pounds per linear foot (0.994 kg/m). Knowing this unit weight allows estimators to convert linear feet of concrete reinforcement runs into total steel weight tonnages for freight shipping and billing. Volume and weight calculations are vital because reinforcing steel is priced and sold by the ton, and delivery trucks are limited by legal gross vehicle weight constraints.

Under ACI 318 structural concrete standards, #4 rebar is commonly specified for residential slab-on-grade grids, driveways, swimming pool shells, and masonry retaining wall cores. Structural steel provides the tensile strength that ready-mix concrete lacks under bending forces. The standard spacing grid for #4 rebar is typically 12 to 18 inches on center, and bars must be elevated on wire or plastic slab chairs to ensure they remain positioned in the middle or bottom third of the slab depth. In retaining walls, #4 vertical bars are placed at 12 or 16 inches on center inside CMU (concrete masonry unit) cells, which are then filled with fluid structural grout to resist lateral soil pressure.

When installing rebar, lap splices are required where runs join. For #4 bars, the standard code lap length is typically 30 to 40 times the bar diameter (amounting to 15 to 20 inches of overlap) to ensure continuous load path transfer. When ordering steel, add a 10% waste margin to cover these splice overlaps and cut scraps. Ensure the steel is free of loose rust, dirt, or oil before concrete is placed.

For GCC/SASO compliance, metric 12mm rebar is frequently specified as the closest local equivalent to #4 bar. While #4 has an exact diameter of 12.7 mm, local manufacturers (such as SABIC) distribute 12mm deformed bars under SASO ISO 6935-2, which have a unit weight of 0.888 kg/m. Structural engineers must adjust their tension reinforcement area calculations (A_s) accordingly, as 12mm bars provide 113 mm² of steel cross-section compared to 129 mm² for a standard ASTM #4 bar.

Worked Example 1 — US Slab-on-Grade:
Calculate the reinforcing steel weight for a 24 ft × 36 ft concrete patio slab. The design specifies #4 rebar in a grid spaced 18 inches (1.5 feet) on center in both directions, with a 3-inch edge clearance.
• Number of runs along 24 ft side: (36 ft ÷ 1.5 ft) + 1 = 25 runs, each 23.5 ft long (subtracting 3" clearance on each end). Total = 587.5 linear feet.
• Number of runs along 36 ft side: (24 ft ÷ 1.5 ft) + 1 = 17 runs, each 35.5 ft long. Total = 603.5 linear feet.
• Total linear footage: 587.5 + 603.5 = 1,191 linear feet.
• Net Steel Weight: 1,191 ft × 0.668 lb/ft = 795.59 lbs.
• Total with 10% lap splice and scrap waste allowance: 795.59 lbs × 1.10 = 875.15 lbs (0.438 short tons).

Worked Example 2 — Metric Masonry Wall (SASO/GCC):
Estimate the weight of SABIC 12mm vertical rebar inside a 3.0-meter-high concrete masonry unit (CMU) retaining wall that is 15 meters long. Bars are spaced 40 cm (0.4m) on center.
• Number of vertical bars: (15 m ÷ 0.4 m) + 1 = 38.5 → 39 bars.
• Single bar length including a 40 cm dowel lap splice at the foundation: 3.0 m + 0.4 m = 3.4 meters.
• Total linear meters: 39 bars × 3.4 m = 132.6 meters.
• Net Mass: 132.6 m × 0.888 kg/m = 117.75 kg.
• Total with 10% waste: 117.75 kg × 1.10 = 129.53 kg.