Carbon Steel Square Bar Weight
Mass per metre and per foot for carbon steel square bar at 7,850 kg/m³ (ASTM A36 / AISI 1018 / EN 10025 S275). Every figure is for the section as drawn. A 6 m length of this size weighs 29.4 kg (65.9 lb per 20 ft).
At the reference dimensions (a = 25 mm) this section has a cross-sectional area of 625.0 mm², giving 4.906 kg/m (3.297 lb/ft). This is the baseline density, so the figures here are what a steel weight chart shows.
Square Bar — formula and derivation
Area of a square bar
A = a²
A = a², where a is the side length
Worked through with the default dimensions:
A = a²A = 25²A = 625.0 mm²
- a
- Side
Weight follows from the area with no further geometry: m = A × 10⁻⁶ × ρ, where A is in mm², ρ in kg/m³ and m in kg/m. At 7,850 kg/m³ that is 4.9063 kg/m for the reference size above.
Carbon steel square bar — size series
| Side | Cross-section | Mass / length |
|---|---|---|
| 6.0 mm | 36.00 mm² · 0.0558 in² | 0.283 kg/m · 0.190 lb/ft |
| 8.0 mm | 64.00 mm² · 0.0992 in² | 0.502 kg/m · 0.338 lb/ft |
| 10 mm | 100.00 mm² · 0.1550 in² | 0.785 kg/m · 0.527 lb/ft |
| 12 mm | 144.00 mm² · 0.2232 in² | 1.130 kg/m · 0.760 lb/ft |
| 16 mm | 256.00 mm² · 0.3968 in² | 2.010 kg/m · 1.350 lb/ft |
| 20 mm | 400.00 mm² · 0.6200 in² | 3.140 kg/m · 2.110 lb/ft |
| 25 mm | 625.00 mm² · 0.9688 in² | 4.906 kg/m · 3.297 lb/ft |
| 30 mm | 900.00 mm² · 1.3950 in² | 7.065 kg/m · 4.747 lb/ft |
| 40 mm | 1,600.00 mm² · 2.4800 in² | 12.560 kg/m · 8.440 lb/ft |
| 50 mm | 2,500.00 mm² · 3.8750 in² | 19.625 kg/m · 13.187 lb/ft |
| 60 mm | 3,600.00 mm² · 5.5800 in² | 28.260 kg/m · 18.990 lb/ft |
| 80 mm | 6,400.00 mm² · 9.9200 in² | 50.240 kg/m · 33.760 lb/ft |
| 100 mm | 10,000.00 mm² · 15.5000 in² | 78.500 kg/m · 52.750 lb/ft |
Computed for Carbon steel at 7850 kg/m³ (0.2836 lb/in³). ASTM A36 / AISI 1018 / EN 10025 S275.
Each row is one nominal size. Because the area is computed from your dimensions rather than read from a mill table, a non-standard size is just as accurate — put it into the calculator above rather than interpolating between rows.
Imperial sizes
Square Bar is also bought in inch sizes. The conversions below are exact (1 in = 25.4 mm by definition), so the metric equivalents are the true millimetre dimensions rather than a rounded nominal figure.
| Stock size | Metric equivalent mm | Cross-section | Mass / length |
|---|---|---|---|
| 1/4 in | 6.35 | 40.32 mm² · 0.0625 in² | 0.317 kg/m · 0.213 lb/ft |
| 3/8 in | 9.52 | 90.73 mm² · 0.1406 in² | 0.712 kg/m · 0.479 lb/ft |
| 1/2 in | 12.70 | 161.29 mm² · 0.2500 in² | 1.266 kg/m · 0.851 lb/ft |
| 5/8 in | 15.88 | 252.02 mm² · 0.3906 in² | 1.978 kg/m · 1.329 lb/ft |
| 3/4 in | 19.05 | 362.90 mm² · 0.5625 in² | 2.849 kg/m · 1.914 lb/ft |
| 1 in | 25.40 | 645.16 mm² · 1.0000 in² | 5.065 kg/m · 3.403 lb/ft |
| 1-1/4 in | 31.75 | 1,008.06 mm² · 1.5625 in² | 7.913 kg/m · 5.317 lb/ft |
| 1-1/2 in | 38.10 | 1,451.61 mm² · 2.2500 in² | 11.395 kg/m · 7.657 lb/ft |
| 2 in | 50.80 | 2,580.64 mm² · 4.0000 in² | 20.258 kg/m · 13.613 lb/ft |
| 2-1/2 in | 63.50 | 4,032.25 mm² · 6.2500 in² | 31.653 kg/m · 21.270 lb/ft |
| 3 in | 76.20 | 5,806.44 mm² · 9.0000 in² | 45.581 kg/m · 30.629 lb/ft |
| 4 in | 101.60 | 10,322.56 mm² · 16.0000 in² | 81.032 kg/m · 54.451 lb/ft |
Stock sizes in inches, converted exactly at 25.4 mm per inch. Material: Carbon Steel at 7850 kg/m³.
The same square bar in every material
Geometry is fixed and only density changes, so this table is the whole material-selection question in one view. Carbon Steel is highlighted. The percentage column is against carbon steel, which is the figure most quotations are built on.
| Material | Density kg/m³ | lb/in³ | Mass / length kg/m | lb/ft | vs carbon steel |
|---|---|---|---|---|---|
| Carbon Steel | 7,850 | 0.2836 | 4.906 | 3.297 | +0.0 % |
| Stainless Steel 304 | 8,000 | 0.2890 | 5.000 | 3.360 | +1.9 % |
| Stainless Steel 316 | 8,000 | 0.2890 | 5.000 | 3.360 | +1.9 % |
| Stainless Steel 316L | 8,000 | 0.2890 | 5.000 | 3.360 | +1.9 % |
| Stainless Steel 430 | 7,700 | 0.2782 | 4.813 | 3.234 | -1.9 % |
| Aluminum 6061-T6 | 2,700 | 0.0975 | 1.688 | 1.134 | -65.6 % |
| Aluminum 5052-H32 | 2,680 | 0.0968 | 1.675 | 1.126 | -65.9 % |
| Aluminum 7075-T6 | 2,810 | 0.1015 | 1.756 | 1.180 | -64.2 % |
| Copper C11000 | 8,940 | 0.3230 | 5.588 | 3.755 | +13.9 % |
| Brass C36000 | 8,500 | 0.3071 | 5.313 | 3.570 | +8.3 % |
| Bronze C93200 | 8,800 | 0.3179 | 5.500 | 3.696 | +12.1 % |
| Titanium Grade 2 | 4,510 | 0.1629 | 2.819 | 1.894 | -42.5 % |
| Gray Cast Iron | 7,200 | 0.2601 | 4.500 | 3.024 | -8.3 % |
| Lead | 11,340 | 0.4097 | 7.088 | 4.763 | +44.5 % |
| Rigid PVC (Type I) | 1,400 | 0.0506 | 0.875 | 0.588 | -82.2 % |
| HDPE (PE 100) | 960 | 0.0347 | 0.600 | 0.403 | -87.8 % |
Same geometry throughout, so the only variable is density. Carbon steel is highlighted as the baseline.
A note on using this table for costing: mass is not price. Aluminium is roughly a third of steel's mass here, but per kilogram it costs several times more, so a straight swap rarely saves money — what it buys is reduced load on a structure or a vehicle.
About carbon steel
The baseline against which every other metal is compared. Mild and medium carbon steels sit at 7,850 kg/m³ across the usual structural and free-machining grades: A36 plate, 1018 shaft, S275JR section. Carbon content moves density so little over the 0.05–0.60 % range that one figure covers the family, which is why mill weight tables for "steel" almost always assume 7,850 kg/m³ (0.2836 lb/in³). Use this entry when the drawing says "steel" and no grade is called out.
- Density
- 7,850 kg/m³ = 0.2836 lb/in³ · 1.0000× carbon steel · typical spread ±1 %
- Specification
- ASTM A36 / AISI 1018 / EN 10025 S275
- Equivalents
- AISI 1018 · EN 1.0401 · JIS SS400 · GB Q235
- Typical uses
- Structural sections · Plate and bar stock · Fabricated weldments · Shafts and pins
Unprotected carbon steel corrodes at roughly 0.1 mm/year in a mild inland atmosphere and far faster in coastal or chemical service, so a corrosion allowance changes the mass you should order — not this density.
About square bar
A square bar has 27.3 % more area than the round bar that circumscribes it (a = d) and 21.5 % more mass — the corners of the square sit outside the circle. The reverse comparison is more useful in practice: a round bar of diameter d fits inside a square of side d with material to spare, so swapping square for round at the same nominal size removes about 21 % of the weight and produces a very similar-looking part.
Specified by side. State whether corners must be sharp or radiused; standard stock usually has a small corner radius.
Download this data
Carbon steel square bar — CSV
Both buttons below read the tables rendered on this page, so the file matches what you are looking at. The full catalogue — all 16 materials across all 10 sections — is on the downloads page.
Fields are quoted per RFC 4180, with a UTF-8 byte-order mark so Excel reads the mm² and · characters correctly. Blank lines separate the weight matrix from the area matrix.
Frequently asked questions
How much does carbon steel square bar weigh?
At the reference dimensions (a = 25 mm) a carbon steel square bar of this size weighs 4.906 kg/m, or 3.297 lb/ft. The table above lists the figure for every standard size so you can read your size directly instead of scaling.
How is the weight of square bar calculated?
Weight is cross-sectional area × length × density. For this shape the area is A = a². At the reference dimensions that gives 625.0 mm², and multiplying by carbon steel's density of 7,850 kg/m³ gives 4.906 kg/m. Nothing is looked up in a table — which is why a non-standard size is calculated just as accurately as a standard one.
Why does carbon steel weigh more or less than steel?
It is the 7,850 kg/m³ baseline that every other figure on this site is measured against. Density is the only variable: the cross-sectional area depends purely on geometry, so a square bar of the same dimensions has the same area in every material and the mass simply scales with density. In this case the ratio is 1.0000× carbon steel.
What is the cross-sectional area of a square bar?
The area depends only on the dimensions, not on the material, so it is identical whichever material you select: at the reference dimensions it is 625.0 mm² (0.9688 in²). That is the number you would enter into a stress or deflection calculation, and it is why changing material on this page never changes the area column.
Does a carbon steel square bar weigh the same as a carbon steel part of a different shape?
No, and the difference is larger than most people expect. At equal nominal size, a square bar is 27.3 % heavier than a round bar, and a hollow section is typically 60–80 % lighter than the solid bar it replaces. Weight follows area, and area changes faster than dimensions do — which is exactly why this needs calculating rather than estimating.
Other materials, same square bar
The same geometry in every material, so the only variable is density.
- SS 304 square bar — 8000 kg/m³
- SS 316 square bar — 8000 kg/m³
- AL 6061 square bar — 2700 kg/m³
- Copper square bar — 8940 kg/m³
- Brass square bar — 8500 kg/m³
- HDPE square bar — 960 kg/m³
- PVC square bar — 1400 kg/m³
- AL 5052 square bar — 2680 kg/m³
Other Carbon steel sections
The same density applied to every shape the site covers.
- Carbon steel round bar — A = π/4 · d²
- Carbon steel hexagonal bar — A = (√3/2) · AF² ≈ 0.8660 · AF²
- Carbon steel flat bar — A = w · t
- Carbon steel plate — A = w · t
- Carbon steel round tube — A = π/4 · (D² − d²), d = D − 2t
- Carbon steel square tube — A = a² − (a − 2t)²
Reference data and tools
- Metal weight overview — how the calculation works
- All 16 materials — densities and specifications
- All 10 sections — formulas and size series
- Density chart — lightest to heaviest
- Metal weight calculator — any size, any material
- All calculators — metal weight and pipe weight
- Download the data — CSV, generated from the same source
- Cross-reference tables — DN / NPS / material equivalents
- Methodology and sources — where every number comes from
Square Bar area from A = a². Mass computed as area × length × density at 7,850 kg/m³ (ASTM A36 / AISI 1018 / EN 10025 S275). No weight on this page is copied from a published table — which is why figures can differ in the last significant digit from a mill's chart calculated at a nominal density.
- Elementary plane geometry. The circle, polygon and hollow-section area formulas.
- ASTM material specifications for each grade named in the material entry (A36, A240/A276, B209/B211/B221, B152/B16/B505, B265/B348, A48, B29, D1784, D3350).
- BIPM / NIST definitional constants: international inch = 25.4 mm, foot = 0.3048 m, pound = 0.45359237 kg.
Dataset version 2026.09.1 · dimensions last verified against source 2026-09-21. Found an error? Report it — corrections are issued with a version bump.