Carbon Steel Round Bar Weight
Mass per metre and per foot for carbon steel round 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 23.1 kg (51.8 lb per 20 ft).
At the reference dimensions (d = 25 mm) this section has a cross-sectional area of 490.9 mm², giving 3.853 kg/m (2.589 lb/ft). This is the baseline density, so the figures here are what a steel weight chart shows.
Round Bar — formula and derivation
Area of a round bar
A = π/4 · d²
A = π/4 × d², where d is the outside diameter
Worked through with the default dimensions:
A = π/4 × d²A = 0.785398 × 25²A = 0.785398 × 625.0A = 490.9 mm²
- d
- Diameter — Outside diameter measured across the bar.
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 3.8534 kg/m for the reference size above.
Carbon steel round bar — size series
| Diameter | Cross-section | Mass / length |
|---|---|---|
| 6.0 mm | 28.27 mm² · 0.0438 in² | 0.222 kg/m · 0.149 lb/ft |
| 8.0 mm | 50.27 mm² · 0.0779 in² | 0.395 kg/m · 0.265 lb/ft |
| 10 mm | 78.54 mm² · 0.1217 in² | 0.617 kg/m · 0.414 lb/ft |
| 12 mm | 113.10 mm² · 0.1753 in² | 0.888 kg/m · 0.597 lb/ft |
| 14 mm | 153.94 mm² · 0.2386 in² | 1.208 kg/m · 0.812 lb/ft |
| 16 mm | 201.06 mm² · 0.3116 in² | 1.578 kg/m · 1.061 lb/ft |
| 20 mm | 314.16 mm² · 0.4869 in² | 2.466 kg/m · 1.657 lb/ft |
| 25 mm | 490.87 mm² · 0.7609 in² | 3.853 kg/m · 2.589 lb/ft |
| 30 mm | 706.86 mm² · 1.0956 in² | 5.549 kg/m · 3.729 lb/ft |
| 32 mm | 804.25 mm² · 1.2466 in² | 6.313 kg/m · 4.242 lb/ft |
| 40 mm | 1,256.64 mm² · 1.9478 in² | 9.865 kg/m · 6.629 lb/ft |
| 50 mm | 1,963.50 mm² · 3.0434 in² | 15.413 kg/m · 10.357 lb/ft |
| 60 mm | 2,827.43 mm² · 4.3825 in² | 22.195 kg/m · 14.915 lb/ft |
| 80 mm | 5,026.55 mm² · 7.7912 in² | 39.458 kg/m · 26.515 lb/ft |
| 100 mm | 7,853.98 mm² · 12.1737 in² | 61.654 kg/m · 41.429 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
Round 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 |
|---|---|---|---|
| 1/8 in | 3.17 | 7.92 mm² · 0.0123 in² | 0.062 kg/m · 0.042 lb/ft |
| 3/16 in | 4.76 | 17.81 mm² · 0.0276 in² | 0.140 kg/m · 0.094 lb/ft |
| 1/4 in | 6.35 | 31.67 mm² · 0.0491 in² | 0.249 kg/m · 0.167 lb/ft |
| 5/16 in | 7.94 | 49.48 mm² · 0.0767 in² | 0.388 kg/m · 0.261 lb/ft |
| 3/8 in | 9.52 | 71.26 mm² · 0.1104 in² | 0.559 kg/m · 0.376 lb/ft |
| 1/2 in | 12.70 | 126.68 mm² · 0.1963 in² | 0.994 kg/m · 0.668 lb/ft |
| 5/8 in | 15.88 | 197.93 mm² · 0.3068 in² | 1.554 kg/m · 1.044 lb/ft |
| 3/4 in | 19.05 | 285.02 mm² · 0.4418 in² | 2.237 kg/m · 1.503 lb/ft |
| 7/8 in | 22.22 | 387.95 mm² · 0.6013 in² | 3.045 kg/m · 2.046 lb/ft |
| 1 in | 25.40 | 506.71 mm² · 0.7854 in² | 3.978 kg/m · 2.673 lb/ft |
| 1-1/4 in | 31.75 | 791.73 mm² · 1.2272 in² | 6.215 kg/m · 4.176 lb/ft |
| 1-1/2 in | 38.10 | 1,140.09 mm² · 1.7671 in² | 8.950 kg/m · 6.014 lb/ft |
| 2 in | 50.80 | 2,026.83 mm² · 3.1416 in² | 15.911 kg/m · 10.691 lb/ft |
| 2-1/2 in | 63.50 | 3,166.92 mm² · 4.9087 in² | 24.860 kg/m · 16.705 lb/ft |
| 3 in | 76.20 | 4,560.37 mm² · 7.0686 in² | 35.799 kg/m · 24.056 lb/ft |
| 4 in | 101.60 | 8,107.32 mm² · 12.5664 in² | 63.642 kg/m · 42.766 lb/ft |
Stock sizes in inches, converted exactly at 25.4 mm per inch. Material: Carbon Steel at 7850 kg/m³.
The same round 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 | 3.853 | 2.589 | +0.0 % |
| Stainless Steel 304 | 8,000 | 0.2890 | 3.927 | 2.639 | +1.9 % |
| Stainless Steel 316 | 8,000 | 0.2890 | 3.927 | 2.639 | +1.9 % |
| Stainless Steel 316L | 8,000 | 0.2890 | 3.927 | 2.639 | +1.9 % |
| Stainless Steel 430 | 7,700 | 0.2782 | 3.780 | 2.540 | -1.9 % |
| Aluminum 6061-T6 | 2,700 | 0.0975 | 1.325 | 0.891 | -65.6 % |
| Aluminum 5052-H32 | 2,680 | 0.0968 | 1.316 | 0.884 | -65.9 % |
| Aluminum 7075-T6 | 2,810 | 0.1015 | 1.379 | 0.927 | -64.2 % |
| Copper C11000 | 8,940 | 0.3230 | 4.388 | 2.949 | +13.9 % |
| Brass C36000 | 8,500 | 0.3071 | 4.172 | 2.804 | +8.3 % |
| Bronze C93200 | 8,800 | 0.3179 | 4.320 | 2.903 | +12.1 % |
| Titanium Grade 2 | 4,510 | 0.1629 | 2.214 | 1.488 | -42.5 % |
| Gray Cast Iron | 7,200 | 0.2601 | 3.534 | 2.375 | -8.3 % |
| Lead | 11,340 | 0.4097 | 5.567 | 3.741 | +44.5 % |
| Rigid PVC (Type I) | 1,400 | 0.0506 | 0.687 | 0.462 | -82.2 % |
| HDPE (PE 100) | 960 | 0.0347 | 0.471 | 0.317 | -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 round bar
Round bar is the only shape whose area grows with the square of a single dimension, so small diameter changes move weight much faster than intuition suggests: going from 25 mm to 28 mm — a 12 % diameter increase — raises the weight per metre by 25 %. This is why shaft stock is normally bought to the nearest preferred diameter rather than machined down from the next size up; the material saved is more than the weight table implies.
Specified by diameter only. For ground and polished stock, add the tolerance class and the straightness limit.
Download this data
Carbon steel round 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 round bar weigh?
At the reference dimensions (d = 25 mm) a carbon steel round bar of this size weighs 3.853 kg/m, or 2.589 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 round bar calculated?
Weight is cross-sectional area × length × density. For this shape the area is A = π/4 · d². At the reference dimensions that gives 490.9 mm², and multiplying by carbon steel's density of 7,850 kg/m³ gives 3.853 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 round 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 round 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 490.9 mm² (0.7609 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 round 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 round bar
The same geometry in every material, so the only variable is density.
- SS 304 round bar — 8000 kg/m³
- SS 316 round bar — 8000 kg/m³
- AL 6061 round bar — 2700 kg/m³
- Copper round bar — 8940 kg/m³
- Brass round bar — 8500 kg/m³
- HDPE round bar — 960 kg/m³
- PVC round bar — 1400 kg/m³
- AL 5052 round bar — 2680 kg/m³
Other Carbon steel sections
The same density applied to every shape the site covers.
- Carbon steel square bar — A = a²
- 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
Round Bar area from A = π/4 · d². 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.