Carbon Steel Flat Bar Weight
Mass per metre and per foot for carbon steel flat 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 14.1 kg (31.6 lb per 20 ft).
At the reference dimensions (w = 50 mm, t = 6 mm) this section has a cross-sectional area of 300.0 mm², giving 2.355 kg/m (1.582 lb/ft). This is the baseline density, so the figures here are what a steel weight chart shows.
Flat Bar — formula and derivation
Area of a flat bar
A = w · t
A = w × t, where w is width and t is thickness
Worked through with the default dimensions:
A = w × tA = 50 × 6A = 300.0 mm²
- w
- Width
- t
- Thickness
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 2.3550 kg/m for the reference size above.
Carbon steel flat bar — size series
| Width | 3.0 | 4.0 | 5.0 | 6.0 | 8.0 | 10 | 12 | 16 | 20 |
|---|---|---|---|---|---|---|---|---|---|
| 12 mm | 0.283 kg/m · 0.190 lb/ft | 0.377 kg/m · 0.253 lb/ft | 0.471 kg/m · 0.316 lb/ft | 0.565 kg/m · 0.380 lb/ft | 0.754 kg/m · 0.506 lb/ft | 0.942 kg/m · 0.633 lb/ft | 1.130 kg/m · 0.760 lb/ft | 1.507 kg/m · 1.013 lb/ft | 1.884 kg/m · 1.266 lb/ft |
| 16 mm | 0.377 kg/m · 0.253 lb/ft | 0.502 kg/m · 0.338 lb/ft | 0.628 kg/m · 0.422 lb/ft | 0.754 kg/m · 0.506 lb/ft | 1.005 kg/m · 0.675 lb/ft | 1.256 kg/m · 0.844 lb/ft | 1.507 kg/m · 1.013 lb/ft | 2.010 kg/m · 1.350 lb/ft | 2.512 kg/m · 1.688 lb/ft |
| 20 mm | 0.471 kg/m · 0.316 lb/ft | 0.628 kg/m · 0.422 lb/ft | 0.785 kg/m · 0.527 lb/ft | 0.942 kg/m · 0.633 lb/ft | 1.256 kg/m · 0.844 lb/ft | 1.570 kg/m · 1.055 lb/ft | 1.884 kg/m · 1.266 lb/ft | 2.512 kg/m · 1.688 lb/ft | 3.140 kg/m · 2.110 lb/ft |
| 25 mm | 0.589 kg/m · 0.396 lb/ft | 0.785 kg/m · 0.527 lb/ft | 0.981 kg/m · 0.659 lb/ft | 1.177 kg/m · 0.791 lb/ft | 1.570 kg/m · 1.055 lb/ft | 1.963 kg/m · 1.319 lb/ft | 2.355 kg/m · 1.582 lb/ft | 3.140 kg/m · 2.110 lb/ft | 3.925 kg/m · 2.637 lb/ft |
| 30 mm | 0.706 kg/m · 0.475 lb/ft | 0.942 kg/m · 0.633 lb/ft | 1.177 kg/m · 0.791 lb/ft | 1.413 kg/m · 0.949 lb/ft | 1.884 kg/m · 1.266 lb/ft | 2.355 kg/m · 1.582 lb/ft | 2.826 kg/m · 1.899 lb/ft | 3.768 kg/m · 2.532 lb/ft | 4.710 kg/m · 3.165 lb/ft |
| 40 mm | 0.942 kg/m · 0.633 lb/ft | 1.256 kg/m · 0.844 lb/ft | 1.570 kg/m · 1.055 lb/ft | 1.884 kg/m · 1.266 lb/ft | 2.512 kg/m · 1.688 lb/ft | 3.140 kg/m · 2.110 lb/ft | 3.768 kg/m · 2.532 lb/ft | 5.024 kg/m · 3.376 lb/ft | 6.280 kg/m · 4.220 lb/ft |
| 50 mm | 1.177 kg/m · 0.791 lb/ft | 1.570 kg/m · 1.055 lb/ft | 1.963 kg/m · 1.319 lb/ft | 2.355 kg/m · 1.582 lb/ft | 3.140 kg/m · 2.110 lb/ft | 3.925 kg/m · 2.637 lb/ft | 4.710 kg/m · 3.165 lb/ft | 6.280 kg/m · 4.220 lb/ft | 7.850 kg/m · 5.275 lb/ft |
| 60 mm | 1.413 kg/m · 0.949 lb/ft | 1.884 kg/m · 1.266 lb/ft | 2.355 kg/m · 1.582 lb/ft | 2.826 kg/m · 1.899 lb/ft | 3.768 kg/m · 2.532 lb/ft | 4.710 kg/m · 3.165 lb/ft | 5.652 kg/m · 3.798 lb/ft | 7.536 kg/m · 5.064 lb/ft | 9.420 kg/m · 6.330 lb/ft |
| 80 mm | 1.884 kg/m · 1.266 lb/ft | 2.512 kg/m · 1.688 lb/ft | 3.140 kg/m · 2.110 lb/ft | 3.768 kg/m · 2.532 lb/ft | 5.024 kg/m · 3.376 lb/ft | 6.280 kg/m · 4.220 lb/ft | 7.536 kg/m · 5.064 lb/ft | 10.048 kg/m · 6.752 lb/ft | 12.560 kg/m · 8.440 lb/ft |
| 100 mm | 2.355 kg/m · 1.582 lb/ft | 3.140 kg/m · 2.110 lb/ft | 3.925 kg/m · 2.637 lb/ft | 4.710 kg/m · 3.165 lb/ft | 6.280 kg/m · 4.220 lb/ft | 7.850 kg/m · 5.275 lb/ft | 9.420 kg/m · 6.330 lb/ft | 12.560 kg/m · 8.440 lb/ft | 15.700 kg/m · 10.550 lb/ft |
Rows: width (mm). Columns: thickness (mm). Computed for Carbon Steel at 7850 kg/m³.
| Width | 3.0 | 4.0 | 5.0 | 6.0 | 8.0 | 10 | 12 | 16 | 20 |
|---|---|---|---|---|---|---|---|---|---|
| 12 mm | 36.0 | 48.0 | 60.0 | 72.0 | 96.0 | 120.0 | 144.0 | 192.0 | 240.0 |
| 16 mm | 48.0 | 64.0 | 80.0 | 96.0 | 128.0 | 160.0 | 192.0 | 256.0 | 320.0 |
| 20 mm | 60.0 | 80.0 | 100.0 | 120.0 | 160.0 | 200.0 | 240.0 | 320.0 | 400.0 |
| 25 mm | 75.0 | 100.0 | 125.0 | 150.0 | 200.0 | 250.0 | 300.0 | 400.0 | 500.0 |
| 30 mm | 90.0 | 120.0 | 150.0 | 180.0 | 240.0 | 300.0 | 360.0 | 480.0 | 600.0 |
| 40 mm | 120.0 | 160.0 | 200.0 | 240.0 | 320.0 | 400.0 | 480.0 | 640.0 | 800.0 |
| 50 mm | 150.0 | 200.0 | 250.0 | 300.0 | 400.0 | 500.0 | 600.0 | 800.0 | 1,000.0 |
| 60 mm | 180.0 | 240.0 | 300.0 | 360.0 | 480.0 | 600.0 | 720.0 | 960.0 | 1,200.0 |
| 80 mm | 240.0 | 320.0 | 400.0 | 480.0 | 640.0 | 800.0 | 960.0 | 1,280.0 | 1,600.0 |
| 100 mm | 300.0 | 400.0 | 500.0 | 600.0 | 800.0 | 1,000.0 | 1,200.0 | 1,600.0 | 2,000.0 |
Area is a property of the geometry alone, so this table is the same for every material. It is what you enter into a stress calculation; the mass table is what you enter into an order.
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.
The same flat 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 | 2.355 | 1.582 | +0.0 % |
| Stainless Steel 304 | 8,000 | 0.2890 | 2.400 | 1.613 | +1.9 % |
| Stainless Steel 316 | 8,000 | 0.2890 | 2.400 | 1.613 | +1.9 % |
| Stainless Steel 316L | 8,000 | 0.2890 | 2.400 | 1.613 | +1.9 % |
| Stainless Steel 430 | 7,700 | 0.2782 | 2.310 | 1.552 | -1.9 % |
| Aluminum 6061-T6 | 2,700 | 0.0975 | 0.810 | 0.544 | -65.6 % |
| Aluminum 5052-H32 | 2,680 | 0.0968 | 0.804 | 0.540 | -65.9 % |
| Aluminum 7075-T6 | 2,810 | 0.1015 | 0.843 | 0.566 | -64.2 % |
| Copper C11000 | 8,940 | 0.3230 | 2.682 | 1.802 | +13.9 % |
| Brass C36000 | 8,500 | 0.3071 | 2.550 | 1.714 | +8.3 % |
| Bronze C93200 | 8,800 | 0.3179 | 2.640 | 1.774 | +12.1 % |
| Titanium Grade 2 | 4,510 | 0.1629 | 1.353 | 0.909 | -42.5 % |
| Gray Cast Iron | 7,200 | 0.2601 | 2.160 | 1.451 | -8.3 % |
| Lead | 11,340 | 0.4097 | 3.402 | 2.286 | +44.5 % |
| Rigid PVC (Type I) | 1,400 | 0.0506 | 0.420 | 0.282 | -82.2 % |
| HDPE (PE 100) | 960 | 0.0347 | 0.288 | 0.194 | -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 flat bar
Flat bar is where the site’s most common estimating mistake shows up: weight is independent of how the bar is oriented, but stiffness is not. A 50 × 6 flat bent about its strong axis is roughly 69 times stiffer than the same bar bent about its weak axis, while both weigh 2.36 kg/m. Reading weight off a flat-bar table tells you what to order; it tells you nothing about whether the section will carry the load.
Specified as width × thickness. Edge condition (square, radiused, or sheared) changes the effective area slightly, not the nominal weight.
Download this data
Carbon steel flat 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 flat bar weigh?
At the reference dimensions (w = 50 mm, t = 6 mm) a carbon steel flat bar of this size weighs 2.355 kg/m, or 1.582 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 flat bar calculated?
Weight is cross-sectional area × length × density. For this shape the area is A = w · t. At the reference dimensions that gives 300.0 mm², and multiplying by carbon steel's density of 7,850 kg/m³ gives 2.355 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 flat 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 flat 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 300.0 mm² (0.4650 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 flat 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 flat bar
The same geometry in every material, so the only variable is density.
- SS 304 flat bar — 8000 kg/m³
- SS 316 flat bar — 8000 kg/m³
- AL 6061 flat bar — 2700 kg/m³
- Copper flat bar — 8940 kg/m³
- Brass flat bar — 8500 kg/m³
- HDPE flat bar — 960 kg/m³
- PVC flat bar — 1400 kg/m³
- AL 5052 flat 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 square bar — A = a²
- Carbon steel hexagonal bar — A = (√3/2) · AF² ≈ 0.8660 · AF²
- 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
Flat Bar area from A = w · t. 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.