Rebar Size Chart
Every standard reinforcing bar size with diameter, area and weight, in both imperial and metric units.
Quick answer
Rebar numbers are the diameter in eighths of an inch: #3 = 3/8 in, #4 = 1/2 in, #5 = 5/8 in, #6 = 3/4 in, #8 = 1 in. #4 and #5 are the usual residential slab and footing bars. Weight runs 0.376 lb/ft for #3 up to 2.670 lb/ft for #8.
Rebar sizes — ASTM A615
Nominal dimensions. Deformations add to the outside dimension but not to the nominal diameter used in design.
| Bar size | Metric | Diameter (in) | Diameter (mm) | Area (sq in) | Weight (lb/ft) | Weight (kg/m) |
|---|---|---|---|---|---|---|
| #3 | 10M | 0.375 | 9.5 | 0.11 | 0.376 | 0.560 |
| #4 | 13M | 0.500 | 12.7 | 0.20 | 0.668 | 0.994 |
| #5 | 16M | 0.625 | 15.9 | 0.31 | 1.043 | 1.552 |
| #6 | 19M | 0.750 | 19.0 | 0.44 | 1.502 | 2.235 |
| #7 | 22M | 0.875 | 22.2 | 0.60 | 2.044 | 3.042 |
| #8 | 25M | 1.000 | 25.4 | 0.79 | 2.670 | 3.973 |
| #9 | 29M | 1.128 | 28.7 | 1.00 | 3.400 | 5.060 |
| #10 | 32M | 1.270 | 32.3 | 1.27 | 4.303 | 6.404 |
| #11 | 36M | 1.410 | 35.8 | 1.56 | 5.313 | 7.907 |
| #14 | 43M | 1.693 | 43.0 | 2.25 | 7.650 | 11.384 |
| #18 | 57M | 2.257 | 57.3 | 4.00 | 13.600 | 20.239 |
Published standard — source: ASTM A615 nominal bar dimensions
Source & method: Metric and kg/m columns are exact conversions of the published imperial values.
Steel area by bar size and spacing
| Bar | 6" o.c. | 8" o.c. | 10" o.c. | 12" o.c. | 16" o.c. | 18" o.c. | 24" o.c. |
|---|---|---|---|---|---|---|---|
| #3 | 0.220 | 0.165 | 0.132 | 0.110 | 0.083 | 0.073 | 0.055 |
| #4 | 0.400 | 0.300 | 0.240 | 0.200 | 0.150 | 0.133 | 0.100 |
| #5 | 0.620 | 0.465 | 0.372 | 0.310 | 0.232 | 0.207 | 0.155 |
| #6 | 0.880 | 0.660 | 0.528 | 0.440 | 0.330 | 0.293 | 0.220 |
| #7 | 1.200 | 0.900 | 0.720 | 0.600 | 0.450 | 0.400 | 0.300 |
| #8 | 1.580 | 1.185 | 0.948 | 0.790 | 0.593 | 0.527 | 0.395 |
Source & method: Computed as bar area × 12 / spacing. Structural adequacy is a design question for a licensed engineer, not a chart lookup.
Frequently asked
- How is rebar size numbered?
- Imperial bar numbers are the diameter in eighths of an inch. A #4 bar is 4/8 or 0.5 inches, a #5 bar is 5/8 or 0.625 inches, and a #8 bar is 8/8 or 1 inch. Above #8 the numbering continues but the eighths rule still holds.
- What is the most common rebar size?
- #4 (0.5 inch) and #5 (0.625 inch) bars dominate residential slabs, footings and driveways. #3 is used for stirrups and light slab mesh replacement, while #6 and larger appear in commercial footings, columns and walls.
- How much does rebar weigh?
- #3 is 0.376 lb per foot, #4 is 0.668 lb per foot, #5 is 1.043 lb per foot and #8 is 2.670 lb per foot. Multiply by total length to estimate a load.
- What does the metric rebar designation mean?
- Soft metric designations give the nominal diameter in millimetres: 10M is 9.5 mm (#3), 13M is 12.7 mm (#4), 16M is 15.9 mm (#5). They label the same bars, not different products.
- Why does rebar cross-sectional area matter?
- Structural design specifies a required steel area per foot of section. Knowing the area of each bar lets you work out how many bars at what spacing satisfy the specification.
Rebar tools and accessories
Rebar tools and accessories
For placing the bar sizes above.
- Rebar tie wire & twisterTie bars at the spacing your drawing calls for.Check price on Amazon →
- Rebar cutter / benderCut and bend #3 through #6 bar on site.Check price on Amazon →
- Rebar chairs & spacersHold cover depth while the pour goes in.Check price on Amazon →
Links go to Amazon search results, not a single listing — confirm ratings, insulation type and listing details before buying, and make sure the part is approved for your application.
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