ASTM A615 · Reinforcing bar
Diameter, weight per foot, and cross-sectional area for #3 through #18 reinforcing bar — the numbers you need to take off quantities and order steel.
| Bar size | Diameter (in) | Diameter (mm) | Weight (lb/ft) | Area (in²) |
|---|---|---|---|---|
| #3 | 0.375 | 9.5 | 0.376 | 0.11 |
| #4 | 0.500 | 12.7 | 0.668 | 0.20 |
| #5 | 0.625 | 15.9 | 1.043 | 0.31 |
| #6 | 0.750 | 19.1 | 1.502 | 0.44 |
| #7 | 0.875 | 22.2 | 2.044 | 0.60 |
| #8 | 1.000 | 25.4 | 2.670 | 0.79 |
| #9 | 1.128 | 28.7 | 3.400 | 1.00 |
| #10 | 1.270 | 32.3 | 4.303 | 1.27 |
| #11 | 1.410 | 35.8 | 5.313 | 1.56 |
| #14 | 1.693 | 43.0 | 7.650 | 2.25 |
| #18 | 2.257 | 57.3 | 13.600 | 4.00 |
Imperial (inch-pound) bar designations per ASTM A615/A615M. The bar number is the diameter in eighths of an inch for #3–#8 (e.g., #5 = 5/8"). Weights are nominal; area is the nominal cross-sectional area.
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U.S. reinforcing bar is sized by a bar number. For #3 through #8 the number is the nominal diameter in eighths of an inch — a #5 bar is 5/8" (0.625"). Larger bars (#9, #10, #11, #14, #18) continue the sequence with their own diameters.
The two numbers you use most: weight per foot for ordering and tonnage takeoffs, and cross-sectional area for matching the structural drawings' required steel (As). Lap splices, development length, and clear cover come from the structural drawings and ACI 318.
Field PM keeps your concrete and reinforcement QA/QC — pour cards, inspection logs, and photos — in the job book, and the concrete calculator handles the yardage for the pour.
For #3 through #8, the bar number is the nominal diameter in eighths of an inch — a #4 bar is 4/8" (0.5") and a #5 is 5/8" (0.625"). Above #8 the numbering continues (#9, #10, #11, #14, #18) but the simple eighths rule no longer holds exactly.
A #4 bar has a nominal diameter of 0.500 inches (12.7 mm), weighs 0.668 lb per foot, and has a cross-sectional area of 0.20 in².
A #8 bar has a nominal diameter of 1.000 inch (25.4 mm), weighs 2.670 lb per foot, and has a cross-sectional area of 0.79 in². It is the largest bar where the "number = eighths of an inch" rule still holds exactly (8/8" = 1").
Nominal weights: #3 = 0.376, #4 = 0.668, #5 = 1.043, #6 = 1.502, #7 = 2.044, #8 = 2.670 lb/ft. Multiply by the total linear feet to estimate tonnage for ordering.
Soft-metric bars use the diameter in millimeters: #3 ≈ #10M (9.5 mm), #4 ≈ #13M, #5 ≈ #16M, #6 ≈ #19M, #8 ≈ #25M. The steel is identical; only the designation differs.
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