Rebar Weight and Size Calculator

A rebar weight and size calculator returns the nominal diameter, weight per foot, and total weight in pounds and tons for a chosen US bar size. Weight per foot depends on bar size, not steel grade, and total weight is the length multiplied by that figure.

Last reviewed September 2026Method & sources Report an error

Nominal Diameter

0.500 in

Breakdown
Nominal Diameter	0.500 in
Weight per Foot	0.668 lb/ft
Total Weight	66.8 lb
Total Weight	0.033 tons
Estimated Cost

How to Calculate Rebar Weight and Size

US rebar sizing is straightforward for the common sizes. The bar number is its diameter in eighths of an inch. A #4 bar is 4/8 = 0.500 in., and a #8 bar is 8/8 = 1.000 in. Above #8, the numbering convention shifts to track cross-sectional area instead. A #9 bar has exactly 1.00 sq in. of area, giving it a 1.128 in. diameter. Weight per foot is fixed by nominal diameter alone and doesn't change with steel grade (40, 60, 75, 80, or 100). This calculator uses the standard weight-per-foot figures from ASTM A615, the US specification for deformed and plain carbon-steel reinforcing bars, also reproduced in CRSI's Manual of Standard Practice. Total weight is simply length × weight per foot.

Example: 100 feet of #4 rebar

100 feet of #4 rebar: 1. #4 bar's standard weight per foot (ASTM A615): 0.668 lb/ft 2. Total weight: 100 × 0.668 = 66.8 lb (0.033 tons) For comparison, the same 100 ft in #8 bar (1.000 in. diameter, 2.670 lb/ft) would weigh 267 lb, four times as much, since weight scales with cross-sectional area, not diameter.

What Is Rebar Weight and Size?

A rebar weight and size calculator is a quick reference for the standard dimensions of US reinforcing bar sizes (#3 through #18), plus a total-weight conversion for a given length. It answers two different questions at once. One is "how big is a #5 bar," which is useful for reading a plan or spec. The other is "how much does 200 feet of #5 bar weigh," which is useful for hauling, shipping cost, or comparing against a per-ton steel price.

Rebar Weight and Size: What a Pro Checks

Use the bar number itself to picture size on a plan. For #3 through #8, the number is the diameter in eighths of an inch, so a #6 bar is 6/8 = 0.750 in. across.
Don't assume a higher-grade bar (60, 75, or 100) weighs more. Grade is yield strength, not size, and weight per foot is fixed by nominal diameter alone per ASTM A615.
Remember the numbering convention shifts above #8. From #9 up, the number tracks cross-sectional area in hundredths of a square inch instead of eighths-of-an-inch diameter, which is why #9's 1.128 in. diameter looks less round.

Frequently Asked Questions

How is rebar size numbered?

For sizes #3 through #8, the number is the bar's diameter in eighths of an inch. A #6 bar is 6/8 = 0.750 in. across. From #9 up, the number instead corresponds to a bar with that many hundredths of a square inch of cross-sectional area. A #9 bar has 1.00 sq in. of area, which is why the diameter progression looks less even above #8.

How much does a piece of rebar weigh?

It depends only on the bar size and length. Weight per foot is fixed by nominal diameter and doesn't change with steel grade. A #4 bar (1/2 in.) weighs 0.668 lb per foot, and a #8 bar (1 in.) weighs 2.670 lb per foot. Multiply the per-foot figure by your total length for the total weight.

Does rebar grade (40, 60, 75) affect its weight?

No. Grade refers to the steel's yield strength (minimum PSI it can resist before permanently deforming), not its physical dimensions. Weight per foot is set entirely by the bar's nominal diameter per ASTM A615, regardless of grade.

What size rebar do I need for my project?

This calculator looks up dimensions and weight for a bar size you already know or have specified. It doesn't determine which size to use, since that depends on the structural load, span, and your local building code or an engineer's design. #3 and #4 are common for residential slabs-on-grade and small footings. Larger structural elements typically call for #5 and up.

Why does #9 have a diameter of 1.128 in. instead of a rounder number?

Because from #9 upward, US rebar sizing switches from "diameter in eighths of an inch" to "cross-sectional area in hundredths of a square inch." A #9 bar is defined to have exactly 1.00 sq in. of area. The 1.128 in. diameter is the one that produces that area. It isn't a rounding artifact. It's how the size is defined.

Sources

ASTM International, A615/A615M: Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement (nominal diameter and weight per size) (opens in a new tab)

Concrete & Masonry