Flat Bar Weight Calculator

Size (W × T)	Area (in²)	lb per ft (steel)
1″ × 1/8″	0.125	0.43
1″ × 1/4″	0.250	0.85
1-1/2″ × 1/4″	0.375	1.28
2″ × 1/4″	0.500	1.70
2″ × 3/8″	0.750	2.55
3″ × 1/4″	0.750	2.55
3″ × 1/2″	1.500	5.10
4″ × 1/2″	2.000	6.81
6″ × 1/2″	3.000	10.21
6″ × 1″	6.000	20.42

Material	lb/in³	g/cm³
Steel (mild/carbon)	0.2836	7.85
Stainless Steel (304)	0.289	8.00
Aluminum (6061)	0.0975	2.70
Brass (C360)	0.307	8.50

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Walk-through

How to Use This Calculator

5 steps

1

Enter the width

Enter the flat bar's width in inches or millimeters, using the unit toggle. Width is the wider of the bar's two rectangular cross-section dimensions.

2

Enter the thickness

Enter the flat bar's thickness in the same unit as width. Thickness is the shorter dimension of the rectangular cross-section.

3

Pick a material

Choose the flat bar material from the Material dropdown. The calculator looks up a standard reference density for steel, stainless steel, aluminum, or brass.

4

Enter the length

Enter the flat bar's length in inches, feet, millimeters, or meters.

5

Read the result

The result updates instantly, showing total weight in pounds and kilograms, plus weight per foot, the cross-section area, and the material density used so you can double-check the math.

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Reference

Formula & Methodology

2 formulas

Weight from cross-section area, length, and density

Weight = Width × Thickness × Length × Density

A flat bar's cross-section is a simple rectangle: width times thickness. Multiply that area by the bar's length to get volume, then by the material's density to get weight.

Weight per foot

Weight per foot = Width × Thickness × 12 in × Density

Weight per foot depends only on the bar's cross-section and material — not on the total length — so it's a fixed rate you can multiply by any run length.

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Glossary

Key Terms Explained

6 terms

Flat bar Steel, aluminum, or other metal stock with a rectangular cross-section, sold by width and thickness (e.g., a "2 by 1/4" flat bar is 2 inches wide and 1/4 inch thick).

Cross-sectional area The area you'd see if you cut the bar straight across — for flat bar, simply width multiplied by thickness, expressed in square inches (in²).

Density Mass per unit volume, expressed here as pounds per cubic inch (lb/in³) or grams per cubic centimeter (g/cm³). Denser materials — like brass — weigh more than lighter materials like aluminum for the same bar dimensions.

Weight per foot The bar's weight for a one-foot length, useful for estimating shipping weight or material cost on a run of any length without recalculating from scratch.

Bar stock Metal sold in long, uniform-cross-section lengths — flat bar, round bar, square bar, and angle iron are all common bar stock shapes, distinguished by their cross-section.

Material The metal alloy the flat bar is made from. This calculator supports steel (mild/carbon), stainless steel (304), aluminum (6061), and brass (C360), each with a different standard reference density.

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Scenarios

Real-World Examples

3 worked examples

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Metal fabricator

2 in x 1/4 in steel flat bar, 20 feet

Width 2 in Thickness 0.25 in Material Steel (mild/carbon) Length 20 ft

A 2 in wide, 1/4 in thick steel flat bar has a cross-section of 0.5 in². Over 20 feet (240 in), that's 120 in³ of steel — about 34 lb (15.4 kg) total, or about 1.7 lb per foot.

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Hobbyist building an aluminum frame

1.5 in x 1/8 in aluminum flat bar, 10 feet

Width 1.5 in Thickness 0.125 in Material Aluminum (6061) Length 10 ft

A 1.5 in wide, 1/8 in thick aluminum bar has a cross-section of 0.1875 in². At aluminum's lighter 0.0975 lb/in³ density, that's roughly 0.22 lb/ft, or about 2.2 lb for the full 10-foot run — less than a quarter of what the same size would weigh in steel.

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Estimating shipping weight per foot

Comparing weight per foot across materials at a fixed size

Width 3 in Thickness 0.5 in

At 3 in x 1/2 in (1.5 in² cross-section), steel runs about 5.1 lb/ft, stainless steel about 5.2 lb/ft, aluminum about 1.7 lb/ft, and brass about 5.5 lb/ft — the Per Foot tab shows this comparison instantly for whatever width and thickness you enter on the Weight tab.

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Deep Dive

Understanding the Flat Bar Weight Calculator

3 chapters · 3 min read

Knowing how much a flat bar weighs — before you order it, ship it, or build with it — matters for shipping quotes, structural support, and material cost estimates. This calculator reduces any flat bar to a rectangular cross-section area times a length, then multiplies by the material's density to get weight.

How the calculation works

A flat bar's cross-section is a simple rectangle: width times thickness. Multiply that area by the bar's length to get volume, and multiply volume by the material's density to get weight. Unlike round or tube stock, there's no need to account for an inner diameter or wall thickness — flat bar is solid, so the formula stays simple: weight = width × thickness × length × density. Density figures come from standard engineering reference tables (MatWeb / eFunda) for each material's most common grade.

Common flat bar sizes

Flat bar stock is typically sold in standard fractional-inch width and thickness combinations, ranging from small sizes like 1 in x 1/8 in up to larger structural sizes like 6 in x 1 in. The Reference Table tab lists common sizes alongside their steel weight per foot, which you can plug straight into the Weight tab or use to sanity-check a supplier's quote.

Choosing the right material and comparing options

The Per Foot tab shows how the same bar dimensions weigh in each of the four supported materials — steel, stainless steel, aluminum, and brass — side by side. This is useful when deciding between materials for the same job: aluminum is roughly a third the weight of steel at the same dimensions, which matters for handling and structural load, while stainless steel and brass carry a small weight premium over mild steel due to their slightly higher densities.

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Questions

Frequently Asked Questions

6 questions

What is the flat bar weight formula?+

Weight equals width times thickness times length times material density. Width and thickness give the cross-section area, which is multiplied by length to get volume, then by density to get weight.

Does it show weight per foot?+

Yes. The result detail shows weight per foot alongside the total weight, and the Per Foot tab compares weight per foot across all four supported materials at your entered width and thickness.

What materials does this calculator support?+

Steel (mild/carbon), stainless steel (304), aluminum (6061), and brass (C360), each using a standard engineering reference density.

What are common flat bar sizes?+

Flat bar stock is commonly sold from about 1 inch by 1/8 inch up to 6 inches by 1 inch, in standard fractional-inch width and thickness increments. See the Reference Table tab for common sizes and their weight per foot in steel.

Does this calculator use pounds or kilograms?+

Both. The main result displays in pounds with the kilogram equivalent shown alongside it, so you can read whichever unit your supplier or spec sheet uses.

Is angle iron calculated the same way?+

No. Angle iron has an L-shaped cross-section instead of a simple rectangle, so it needs a different area formula that accounts for both legs of the L. Use the dedicated Angle Iron Weight Calculator for that shape.

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