How to Calculate Metal Weight: The Complete Guide

Metal weight is volume times density — but the work is getting the volume right for each shape (bar, plate, tube, sheet) and using the correct density for the alloy. Weight drives shipping cost, crane capacity, and price, since metal is sold by weight. This guide covers the shapes and metals the calculator handles.

The 60-second version

Weight = volume × density. Everything else is finding the volume.
Steel ≈ 0.284 lb/in³ (7,850 kg/m³); aluminum ≈ 0.098 lb/in³; the alloy matters.
Round bar volume = π × r² × length; plate = L × W × thickness.
Tube = outer volume − inner volume (the hollow center is not metal).
Keep units consistent — convert everything to inches (or all to mm) first.
Metal is sold by weight, so weight = shipping + price.

What's inside

Volume × density
Densities by metal
Volume by shape
Tubes & pipe
Sheet & gauge
Units & conversions
Why weight matters

1 · Volume × density

The whole calculation is one idea: a piece of metal weighs its volume times the density of the material. Get the volume of the shape in cubic inches (or cubic centimeters), multiply by the density in pounds per cubic inch (or grams per cm³), and you have the weight. The only complications are computing volume for each profile and choosing the right density.

The core formula

Weight = Volume × Density

Consistent units: in³ × lb/in³ = lb, or cm³ × g/cm³ = g. Never mix.

2 · Densities by metal

Density is fixed by the material, so use the value for your specific metal or alloy:

Common metal densities
Metal	lb/in³	g/cm³
Carbon / mild steel	0.284	7.85
Stainless steel (304)	0.289	8.00
Aluminum (6061)	0.098	2.70
Copper	0.323	8.96
Brass	0.307	8.50
Titanium	0.163	4.51

3 · Volume by shape

Each profile has its own volume formula; length is along the bar:

Volume by profile

Round bar = π × radius² × length
Square bar = side² × length
Rectangular bar / plate = width × thickness × length
Hexagonal bar = 0.866 × width² × length

Width across flats for hex. Always convert diameter to radius (÷2) for round stock.

A 1-inch-diameter steel round bar, 10 ft long

Length = 120 in. Volume = π × 0.5² × 120 = 94.2 in³. Weight = 94.2 × 0.284 = 26.8 lb. Switch to aluminum (0.098) and the same bar is just 9.2 lb.

4 · Tubes & pipe

Hollow sections are the one place beginners go wrong: a tube's weight is the metal only, so you subtract the hollow core. Compute the outer volume and the inner (bore) volume, and the difference is the metal.

Tube / pipe weight

Metal volume = (π × R_outer² − π × R_inner²) × length
R_inner = R_outer − wall thickness

A 2-in OD tube with ¼-in wall: R_out = 1, R_in = 0.75. Area = π(1² − 0.75²) = 1.374 in². × length × density.

5 · Sheet & gauge

Sheet metal is plate by another name — length × width × thickness × density — but thickness is often given as a gauge number rather than a decimal. Gauge-to-thickness differs by metal (a 16-gauge steel sheet and 16-gauge aluminum are different thicknesses), so convert gauge to actual thickness for that metal before calculating.

Gauge is not universal

The same gauge number means different thicknesses for steel, stainless, and aluminum. Always convert gauge → decimal thickness using the chart for your specific metal.

6 · Units & conversions

Useful metal-weight conversions
From	To	Multiply by
lb	kg	× 0.4536
in³	cm³	× 16.387
lb/in³	g/cm³	× 27.68
kg/m³	g/cm³	÷ 1000

7 · Why weight matters

Weight is the practical bottom line: metal is priced and sold by the pound or kilogram, shipping is weight-based, and lifting or crane capacity is a safety limit. Knowing the weight before you order tells you the cost, whether a load is legal on a truck, and whether two people can carry a piece or it needs equipment.

Use the metal weight calculator to compute weight for any shape and alloy, remembering to subtract the bore for tubes and to convert gauge to thickness for sheet.