Round Bar Weight Calculator

Weight per Meter Reference (Carbon Steel)

Weight per meter for common round bar diameters (carbon steel, density 7850 kg/m3):

6 mm: 0.222 kg/m | 8 mm: 0.395 kg/m | 10 mm: 0.617 kg/m | 12 mm: 0.888 kg/m | 16 mm: 1.58 kg/m | 20 mm: 2.47 kg/m | 25 mm: 3.85 kg/m | 32 mm: 6.31 kg/m | 40 mm: 9.87 kg/m | 50 mm: 15.4 kg/m | 60 mm: 22.2 kg/m | 80 mm: 39.5 kg/m | 100 mm: 61.7 kg/m.

Formula: W (kg/m) = pi x (D/2)^2 x rho / 1,000,000 with D in mm and rho in kg/m3.

Worked Example: 20 mm Rebar

Estimate the weight of a 12 m long, 20 mm diameter carbon steel rebar.

Step 1 - cross-section area: A = pi x (20/2)^2 = 314.2 mm2 = 3.142 x 10^-4 m2.

Step 2 - volume: V = A x L = 3.142 x 10^-4 x 12 = 3.770 x 10^-3 m3.

Step 3 - weight: W = V x rho = 3.770 x 10^-3 x 7850 = 29.6 kg.

Check: 2.47 kg/m x 12 m = 29.6 kg. The bar weighs approximately 29.6 kg.

Unit Conversion Guide

Weight: 1 kg = 2.20462 lb; 1 tonne = 1000 kg = 2204.6 lb.

Weight per meter: 1 kg/m = 0.67197 lb/ft; 1 lb/ft = 1.488 kg/m.

Diameter: 1 mm = 0.03937 in; 1 in = 25.4 mm.

Length: 1 m = 3.281 ft.

Example: a 50 mm bar at 15.4 kg/m = 15.4 x 0.67197 = 10.35 lb/ft.

Round Bar for Shaft and Machining Stock

Round bar is a common raw material for turned shafts, pins, rollers and fasteners. For machining stock, order bar with a machining allowance (typically 3-6 mm oversize for turned shafts) and estimate weight from the nominal diameter so the stock order covers the finished part plus scrap. Common machining stock sizes: 20, 25, 30, 40, 50, 60, 80 and 100 mm. Bright (cold-drawn) bar has tighter tolerances and a better surface finish than hot-rolled bar; both use the same density for weight estimating.