Pick a US bar size, a stick length, and a piece count. This returns the theoretical bundle weight from the ASTM A615 nominal table — the same lb/ft a yard uses to quote steel. It does not replace a mill test report or the ASTM stamp on the bar.
For US bars #3 through #8, the bar number is the nominal diameter in eighths of an inch. A #4 is 4/8 = 0.500 in. A #8 is 1.000 in.
A plain round of that diameter, in steel at 0.2833 lb/in³, has a theoretical unit weight:
Wlb/ft = 2.670 × din²
because 0.2833 lb/in³ × 12 × π/4 = 2.670 lb/ft per square inch of diameter. A 1 in round is 2.670 lb/ft, which is why #8 is listed at 2.670.
That identity is the physics. This page does not recompute it for every ticket. It multiplies your footage by the published ASTM A615 Table 1 nominal weight (the same figures mill catalogs and CRSI-style charts reprint). For #3–#8 the formula and the table agree to a thousandth of a pound. For #9, #10, #11, #14, and #18 the designation is no longer exact eighths — those bars are sized to round areas of 1.00, 1.27, 1.56, 2.25, and 4.00 in² — so the table is the source, not N/8.
total lb = pieces × lengthft × Wtable × (1 + waste/100)
kilograms = pounds × 0.45359237 · total feet = pieces × lengthft
Deformed bar is not a smooth cylinder. ASTM treats the nominal diameter as that of a plain round with the same weight per foot. Ribs, mill tolerance, and grade (40 / 60 / 80 — yield, not density) are why a scale and a mill cert still matter on the job.
| Bar | d, in | 2.670 × d² | Table, lb/ft |
|---|---|---|---|
| #3 | 0.375 | 0.3755 | 0.376 |
| #4 | 0.500 | 0.6675 | 0.668 |
| #5 | 0.625 | 1.0430 | 1.043 |
| #6 | 0.750 | 1.5019 | 1.502 |
| #7 | 0.875 | 2.0442 | 2.044 |
| #8 | 1.000 | 2.6700 | 2.670 |
| #9 | 1.128 | 3.397 | 3.400 |
| #10 | 1.270 | 4.306 | 4.303 |
| #11 | 1.410 | 5.308 | 5.313 |
| #14 | 1.693 | 7.653 | 7.650 |
| #18 | 2.257 | 13.601 | 13.60 |
The calculator uses the table column. Figures follow ASTM A615/A615M Table 1 as reprinted by mill catalogs (e.g. Re-Steel Supply conversion table). #14 and #18 are printed in the spec as 7.65 and 13.60 lb/ft.
| Pieces | Size | Length | Arithmetic | Weight |
|---|---|---|---|---|
| 10 | #4 | 20 ft | 10 × 20 × 0.668 | 133.6 lb (60.60 kg) |
| 10 | #5 | 20 ft | 10 × 20 × 1.043 | 208.6 lb (94.62 kg) |
| 10 | #4 | 20 ft + 5% waste | 133.6 × 1.05 | 140.28 lb |
Those rows were computed independently in Python against the table above and match this page on load (#4 × 20 ft × 10 pcs). Switch the size to #5 to see 208.6 lb. A scale reading on real deformed bar can differ by mill tolerance; this is takeoff weight, not a certificate.
For #3 through #8, the number is the diameter in eighths of an inch. #3 is 3/8 in, #4 is 1/2 in, #8 is 1 in. Larger sizes (#9, #10, #11, #14, #18) keep a number for convenience but use the published nominal diameters 1.128, 1.270, 1.410, 1.693, and 2.257 in, sized so the cross-section is a round 1.00, 1.27, 1.56, 2.25, or 4.00 in².
You can, and for #3–#8 you will land on the table after ordinary rounding (a #4 comes out 0.6675 lb/ft; the spec lists 0.668). Yards, estimators, and mill catalogs order from the published nominal, not from a fresh π. On #9 and up, using N/8 as the diameter is the wrong geometry — a #10 is 1.270 in, not 1.250 in — so the table is the number that matches a mill quote.
No. Grade is yield strength. Nominal unit weight is a size property. A #5 Grade 60 and a #5 Grade 80 are both 1.043 lb/ft on the ASTM A615 table. Alloy specs such as A706 use the same nominal sizes and weights.
No. This is theoretical / nominal weight for a takeoff. A mill test report and the grade mark rolled into the bar are what the inspector wants. Do not treat this page as a substitute for either, or for the heat number on a bundle tag.
Leave it blank for a clean theoretical total. Add a few percent when you know you will lap bars, cut around openings, or buy stock lengths longer than the piece you actually place. Five to ten percent is a common field pad; the right number is the one your superintendent already uses, not a number invented here. Waste multiplies the theoretical pounds; it does not change lb/ft.
Enter the length of one piece in the unit you measured. Twenty-foot stock is 20 ft or 240 in — same bar. Mixing a foot tape with the inch setting will inflate the ticket by twelve. Piece count is a count, not a length.
One international avoirdupois pound is 0.45359237 kg. The page shows kilograms so a metric scale or an import invoice can be read without a second conversion. Soft-metric bar labels (10M, 13M, 16M…) are a different designation system; this tool is US #3–#18 only.