#4 Rebar — Diameter, Weight & Area
Deformed reinforcing bar per ASTM A615 / A706
#4 rebar (also written No. 4 or number 4 bar) is 1/2" — 0.5 inches (12.7 mm) — in nominal diameter; the "4" stands for 4/8 of an inch. It weighs 0.668 pounds per foot (0.994 kg/m) with a nominal cross-section of 0.2 in² (129 mm²). A standard 20 ft bar weighs 13.4 lb, a 40 ft bar 26.7 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 | 0.5 in (12.7 mm) |
| Nominal area | 0.2 in² (129 mm²) |
| Weight | 0.668 lb/ft (0.994 kg/m) |
Ordering Numbers
| 20 ft bar | 13.4 lb |
| 40 ft bar | 26.7 lb |
| Bars per US ton (20 ft) | 149 |
Frequently Asked Questions
What is the diameter of #4 rebar?
1/2", i.e. 0.5 inches or 12.7 mm — bar numbers count eighths of an inch, so #4 is nominally 4/8".
How thick is #4 rebar?
Number 4 bar is 1/2" thick (12.7 mm). That is the nominal diameter: the ribs are already included, because the nominal size is defined by mass per foot.
How much does #4 rebar weigh per foot?
0.668 lb per foot (0.994 kg/m). A 20 ft bar weighs 13.4 lb; a US ton is about 149 such bars.
What is the area of #4 rebar?
The nominal cross-section of #4 is 0.2 in² (129 mm²) — the value reinforcement schedules use when summing required steel area.
What is the metric equivalent of #4 rebar?
The closest European size is Ø12 (12 mm, 0.888 kg/m, B500 per EN 10080). Matches are approximate — when substituting, match the required steel area, not the bar count.
What grade is #4 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