Rebar Calculator
#4 Reinforcing Bar
ASTM A615 (US customary) reinforcing bar — diameter 12.7 mm (0.500 in), cross-sectional area, mass per metre, and standard spacing options.
Diameter
12.7 mm
Area
0.196 in²
Perimeter
1.57 in
Mass per metre
0.67 lb/ft
Area per foot width at common spacings
For slab or wall reinforcement specified as “#4@ spacing c/c” — the area provided per unit width at each standard centre-to-centre spacing.
| Spacing | As (in²/ft) |
|---|---|
| #4 @ 4in c/c | 0.589 |
| #4 @ 6in c/c | 0.393 |
| #4 @ 8in c/c | 0.295 |
| #4 @ 9in c/c | 0.262 |
| #4 @ 10in c/c | 0.236 |
| #4 @ 12in c/c | 0.196 |
| #4 @ 16in c/c | 0.147 |
Equivalent options at 6in spacing
Every US bar size at the same reference spacing, so you can see at a glance which other size lands near the same area per unit width as #4.
| Bar | As (in²/ft) |
|---|---|
| #3 | 0.221 |
| #4 (this bar) | 0.393 |
| #5 | 0.614 |
| #6 | 0.884 |
| #7 | 1.203 |
| #8 | 1.571 |
| #9 | 1.999 |
| #10 | 2.534 |
| #11 | 3.123 |
| #14 | 4.502 |
| #18 | 8.002 |
Area and mass are computed directly from the nominal diameter (mass assumes standard steel density, 7850 kg/m³) — the same values the Rebar Calculator uses.
Open #4 in the Rebar Calculator →