Rebar Size Chart: Diameter, Area and Weight per Foot

Rebar size chart: #3 to #8

US bars are named by a number that equals their nominal diameter in eighths of an inch. The chart below covers the sizes used in slabs, footings, walls and driveways. Weights are the nominal values in ASTM A615 as published on Gerdau’s rebar data sheet; diameters, areas and metric conversions are computed from them.

Areas are π × d² ÷ 4 from the nominal diameter. Design tables print them rounded (for example 0.20 in² for #4 and 0.31 in² for #5), so use the table in your project specification or ASTM A615 for design checks. Rebar is deformed (it has ribs), so a caliper across the ribs reads a little more than the nominal diameter; nominal means “the diameter of a plain round bar of the same weight per foot.”

Rebar weight chart: lb per foot and kg per metre

Weight per foot is what you need when a supplier sells by the pound or ton, or when you check a delivery. These are stick weights at nominal weight, plus how much bar a US ton buys.

Total weight (lb) = length (ft) × lb/ft  ·  Mass (kg) = length (m) × kg/m

Sticks per ton are rounded to the nearest stick. Gerdau lists typical stock lengths of 20, 30, 40 and 60 ft; home centers often stock shorter cut lengths, so weigh by the actual length you buy.

Large bars: #9 to #18

Bars above #8 are used in columns, bridges and heavy foundations. From #9 up, the bar number no longer equals the diameter in eighths of an inch, so we list only the published weights here. Get the nominal diameter and area for these sizes from ASTM A615 Table 1 or your engineer’s schedule.

There is no #12, #13, #15, #16 or #17 in the standard series; the jump from #11 to #14 and #18 is normal.

Metric rebar sizes: soft metric vs Canadian M bars

“Metric rebar” means two different things, and mixing them up is the most common chart mistake.

Soft metric (US bars). Many US mills roll the same inch bars but stamp a metric number: #4 is marked 13 (its diameter rounded to millimetres), #5 is 16 and so on. The steel is identical, so the weights in the charts above apply. A “13” bar is a #4.

Canadian metric (CSA G30.18). Canada uses true metric bars named 10M, 15M, 20M and up. They are different bars with their own weights:

A 10M bar weighs 0.785 kg/m against 0.560 kg/m for a US #3 stamped 10, so 100 m of 10M is 78.5 kg and 100 m of #4 (stamped 13) is 99.4 kg. Bars named by plain millimetres (10 mm, 12 mm, 16 mm) in Europe, Australia or Asia follow other national standards; use your supplier’s mass per metre for those.

What size is #3, #4, #5 and #6 rebar?

The four sizes most homeowners and small contractors buy, with everything you need for a takeoff in one place.

#3 rebar

#3 rebar is 3/8 in (9.5 mm) in diameter and weighs 0.376 lb/ft (0.560 kg/m). A 20 ft stick weighs 7.52 lb. Its nominal area is about 0.110 in² (71 mm²). It is the lightest bar in the standard series; whether it is enough for your project is a design question.

#4 rebar

#4 rebar is 1/2 in (12.7 mm) and weighs 0.668 lb/ft (0.994 kg/m), or 13.36 lb per 20 ft stick. Its area is about 0.196 in² (127 mm²), roughly 1.8 times that of #3. It is stamped 13 in soft metric. One US ton of #4 is about 150 sticks.

#5 rebar (5/8 in)

#5 rebar is 5/8 in (15.9 mm), weighs 1.043 lb/ft (1.552 kg/m) and 20.86 lb per 20 ft stick. Area is about 0.307 in² (198 mm²). Soft metric mark: 16. People search “5/8 rebar weight” for this bar: a 40 ft stick is 41.72 lb.

#6 rebar (3/4 in)

#6 rebar is 3/4 in (19.05 mm), weighs 1.502 lb/ft (2.235 kg/m) and 30.04 lb per 20 ft stick. Area is about 0.442 in² (285 mm²). Soft metric mark: 19. At 1.5 lb per foot, a 40 ft stick is about 60 lb.

How do you read the markings on a rebar?

CRSI describes the standard marking sequence rolled into the bar: a letter or symbol for the producing mill, then the bar size, then the steel type (“S” for carbon steel to ASTM A615, “W” for low-alloy weldable steel to ASTM A706), then the grade, either as a number (60, 75, 80, 100 or 120) or as lines (one line for Grade 60, two for 75, three for 80 or 100, four for 120). So a bar marked with a mill letter, “4”, “S” and one line is #4, A615, Grade 60. The size number may be the inch number (4) or the soft metric number (13); both mean the same bar.

Grade is strength, not size. A #4 Grade 60 bar and a #4 Grade 80 bar weigh the same 0.668 lb/ft, so the charts on this page apply to every grade. Gerdau lists A615 in Grades 40, 60, 75, 80 and 100 and A706 in Grades 60 and 80.

How much steel area do common spacings give?

Engineers often specify slab and wall steel as square inches per foot of width (in²/ft). Divide the bar area by the spacing in feet to compare layouts:

Steel area (in²/ft) = bar area (in²) × 12 ÷ spacing (in)

This is only a way to compare two layouts that give the same steel, for example when a supplier is out of one size. It is not a spacing recommendation. Bar size, spacing, edge cover, lap length and chair height for any slab, footing or wall come from your plans, a licensed engineer or your local building department. If you substitute a bar size, get the change approved first.

How to use the chart to estimate a rebar order

1. Count the length. Use the rebar calculator for slab grids, or multiply bars × length for footings and walls. Add an allowance for laps.
2. Convert to sticks. Divide by the stick length and round up.
3. Convert to weight with the lb/ft (or kg/m) column if you buy or haul by weight.

For the concrete around the steel, use the concrete footing calculator or the concrete slab calculator; for block walls with vertical bars, the concrete block calculator.

Common mistakes with rebar sizes

• Reading 13 or 16 as millimetre bars from another standard. On US bars these are soft metric marks for #4 and #5.
• Treating 10M as #3. Canadian 10M weighs about 40% more per metre than #3 (0.785 vs 0.560 kg/m).
• Measuring over the ribs. A caliper on a #4 reads more than 0.5 in; go by the stamped size.
• Using the grade lines as the size. One line means Grade 60, not #1.
• Pricing by weight with the wrong bar. 601 ft of bar is 226 lb in #3 but 401 lb in #4; check the size before converting.

Steel prices change often and vary by region and mill, so we do not publish a national price. Multiply your sticks by the supplier’s price per stick, or the weight from the chart by their price per pound or ton, and add tie wire, chairs and delivery.