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About

In reinforced concrete construction, the accurate estimation of steel tonnage is a prerequisite for budgeting, structural integrity checks, and logistics. Engineers specify reinforcing bars (rebar) by length and count on blueprints, but suppliers quote and ship material by weight (tons or kilograms). Miscalculating this conversion can result in ordering insufficient material for a slab or overpaying for freight.

This calculator provides a precise conversion between linear length and total weight for standard rebar sizes. It covers both the US Imperial system (ASTM A615, sizes #3 through #18) and the European Metric system (DIN 488, 6mm to 50mm). Rather than using a generic density for steel, this tool utilizes the specific linear density values mandated by industry standards, ensuring that your billing weights match the theoretical weights used in contract documents.

rebar calculator reinforcement steel concrete foundation ASTM A615 civil engineering

Formulas

The calculation is based on the linear density (λ) defined by the standard. To find Weight (W) from Length (L):

W = L × λ

To find Length (L) from a given Weight (W):

L = Wλ

Reference Data

Bar Size (Imperial)Diameter (in)Weight (lb/ft)Bar Size (Metric)Diameter (mm)Mass (kg/m)
#30.3750.3766mm60.222
#40.5000.6688mm80.395
#50.6251.04310mm100.617
#60.7501.50212mm120.888
#81.0002.67016mm161.580
#101.2704.30325mm253.853
#141.6937.65032mm326.313
#182.25713.60050mm5015.413

Frequently Asked Questions

The number represents the bar diameter in eighths of an inch. For example, a #4 bar is 4/8 inches, or 1/2 inch in diameter. This rule applies up to #8 bars; larger sizes follow slightly different conventions but are still standardized.
Rebar is not a perfect cylinder; it has deformation ribs to grip concrete. The ASTM and DIN standards define a "nominal weight" that accounts for these deformations, which is what this tool uses rather than pure geometric volume.
The tool separates the standards because the bar sizes do not perfectly align (e.g., a #4 bar is 12.7mm, which is close to but not identical to a 12mm metric bar). You should select the standard that matches your blueprint specifications.
Yes. The weight of the epoxy coating is negligible for general weight estimation purposes. The core steel mass remains the dominant factor.