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Calculate the weight and cost of reinforcement bar (rebar) for concrete construction. Supports standard rebar sizes from #3 to #18 with accurate weight per foot calculations.
Reinforcement bar, commonly known as rebar, is a steel bar or mesh of steel wires used to strengthen and hold concrete in tension. Rebar is essential in reinforced concrete construction because concrete has high compressive strength but relatively low tensile strength. By adding rebar to concrete structures, we significantly increase their ability to withstand tensile forces, bending, and cracking.
The rebar weight calculator helps contractors, engineers, and construction professionals accurately estimate the total weight of rebar needed for their projects. This is crucial for cost estimation, ordering the correct amount of materials, transportation planning, and structural engineering calculations.
Rebar is designated by numbers that indicate the bar diameter in eighths of an inch. For example, #4 rebar has a diameter of 4/8 inch (0.500"), and #8 rebar has a diameter of 8/8 inch (1.000"). The weight per foot increases significantly with larger bar sizes due to the circular cross-sectional area.
Total Weight = Weight per Foot × Length × Quantity
Where:
Diameter (inches) = Bar Number / 8
For example, #4 rebar has a diameter of 4/8 = 0.500 inches. This numbering system makes it easy to remember the approximate diameter of common rebar sizes.
Weight per Foot = (Diameter² / 162.2) pounds
This formula approximates the weight based on steel density (490 lb/ft³) and the circular cross-sectional area. However, actual rebar weights are standardized and slightly different due to manufacturing tolerances and the deformation pattern (ribs) on the rebar surface.
| Bar Size | Diameter (inches) | Weight (lb/ft) | Typical Use |
|---|---|---|---|
| #3 | 0.375" | 0.376 | Light reinforcement, residential slabs |
| #4 | 0.500" | 0.668 | Most common, driveways, patios, slabs |
| #5 | 0.625" | 1.043 | Structural slabs, footings, walls |
| #6 | 0.750" | 1.502 | Heavy-duty slabs, beams, columns |
| #7 | 0.875" | 2.044 | Structural columns, bridge decks |
| #8 | 1.000" | 2.670 | Large structural members, piers |
| #9 | 1.128" | 3.400 | Large beams, heavy construction |
| #10 | 1.270" | 4.303 | Bridge construction, heavy columns |
| #11 | 1.410" | 5.313 | Heavy structural applications |
| #14 | 1.693" | 7.650 | Large foundations, massive structures |
| #18 | 2.257" | 13.600 | Very large structural elements, dams |
Rebar provides essential reinforcement in foundation work, including:
Vertical reinforcement in columns carries compression loads:
Horizontal members require both tension and shear reinforcement:
Floor and roof slabs use rebar grids for distributed loading:
The rebar size depends on the structural requirements, concrete thickness, and load conditions. For residential slabs and driveways, #3 or #4 is typical. For structural applications like beams and columns, #5 to #8 are common. Always consult structural drawings and local building codes. An engineer should specify the exact size, spacing, and placement based on load calculations.
Common rebar spacing in slabs ranges from 12 to 18 inches on center in both directions. For a 4-inch residential slab, #3 or #4 rebar spaced at 18 inches on center is typical. Heavier loads or thicker slabs may require closer spacing (12 inches) or larger bar sizes. Building codes and structural engineers provide specific spacing requirements based on the application.
The most common rebar grades in the US are Grade 40 and Grade 60, where the number indicates the minimum yield strength in ksi (thousand pounds per square inch). Grade 60 (60,000 psi yield strength) is the most widely used for general construction. Grade 40 (40,000 psi) is used for lighter applications. Higher grades like Grade 75 and Grade 80 are available for specialized high-strength applications.
Yes, rebar can be bent on site, but it must be done properly to avoid damaging the bar. Cold bending is common for smaller sizes (#3 to #6) using manual or hydraulic bar benders. Larger bars (#7 and above) may require mechanical benders or pre-bending at the fabrication shop. Never heat rebar to bend it, as this changes the steel properties and reduces strength. Follow minimum bend diameter requirements specified in codes (typically 6 times the bar diameter for standard hooks).
Concrete cover requirements vary by application and exposure conditions. For slabs on grade, minimum cover is typically 2 inches for #5 bars and smaller, and 3 inches for larger bars. For walls and footings cast against earth, 3 inches is standard. Beams and columns exposed to weather require 1.5 to 2 inches. Indoor beams, columns, and slabs need 0.75 to 1.5 inches depending on bar size. Check local building codes for specific requirements.
Epoxy-coated rebar has a green fusion-bonded epoxy coating that provides superior corrosion protection. It's used in environments with high chloride exposure such as bridge decks, parking structures, marine structures, and areas where de-icing salts are used. The coating protects the steel from chloride-induced corrosion, extending the service life of the structure. Epoxy-coated rebar costs about 50-80% more than standard black rebar but significantly extends durability in corrosive environments.
When rebar needs to be extended, bars are overlapped (lapped) and tied together. The lap length depends on the bar size, concrete strength, and stress conditions. Typical lap lengths range from 30 to 60 times the bar diameter. For example, #4 rebar (0.5" diameter) might require a 15 to 30 inch lap. In high-stress areas or where space is limited, mechanical couplers or welded splices can be used instead of laps. Always follow engineering specifications for lap requirements.
Rebar consists of individual steel bars placed and tied together, offering higher strength and better crack control for structural applications. Welded wire mesh (WWM) or welded wire fabric (WWF) comes in rolls or sheets with pre-welded grids, making it faster to install for large slab areas. Mesh is suitable for light-duty applications like residential slabs, sidewalks, and temperature/shrinkage reinforcement. Rebar is preferred for structural members, heavy loads, and anywhere higher strength is needed. The two can be used together in some applications.
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