#18 Rebar — Diameter, Weight & Area
Deformed reinforcing bar per ASTM A615 / A706
#18 rebar (also written No. 18 or number 18 bar) is 2.257" — 2.257 inches (57.33 mm) — in nominal diameter; the "18" stands for 18/8 of an inch. It weighs 13.6 pounds per foot (20.24 kg/m) with a nominal cross-section of 4 in² (2,581 mm²). A standard 20 ft bar weighs 272 lb, a 40 ft bar 544 lb.
These nominal values (per ASTM A615) are what reinforcement schedules, quotes, and delivery tickets use — the deformations are already accounted for in the nominal diameter.
Size & Weight
| Nominal diameter | 2.257 in (57.33 mm) |
| Nominal area | 4 in² (2,581 mm²) |
| Weight | 13.6 lb/ft (20.24 kg/m) |
Ordering Numbers
| 20 ft bar | 272 lb |
| 40 ft bar | 544 lb |
| Bars per US ton (20 ft) | 7 |
Frequently Asked Questions
What is the diameter of #18 rebar?
2.257", i.e. 2.257 inches or 57.33 mm — bar numbers count eighths of an inch, so #18 is nominally 18/8".
How thick is #18 rebar?
Number 18 bar is 2.257" thick (57.33 mm). That is the nominal diameter: the ribs are already included, because the nominal size is defined by mass per foot.
How much does #18 rebar weigh per foot?
13.6 lb per foot (20.24 kg/m). A 20 ft bar weighs 272 lb; a US ton is about 7 such bars.
What is the area of #18 rebar?
The nominal cross-section of #18 is 4 in² (2,581 mm²) — the value reinforcement schedules use when summing required steel area.
What is the metric equivalent of #18 rebar?
The closest European size is Ø40 (40 mm, 9.86 kg/m, B500 per EN 10080). Matches are approximate — when substituting, match the required steel area, not the bar count.
What grade is #18 rebar?
Grade is independent of size: ASTM A615 Grade 40, 60, or 75 (yield in ksi), with Grade 60 the US default. A706 covers weldable low-alloy bars for seismic work.
Values are entered from the governing standard’s published tables and cross-checked programmatically against its mass and section formulas before publication. Spotted an error? Write to advertising@metalabout.net — verified corrections ship within days. About