Gray Cast Iron Hexagonal Bar Weight
Mass per metre and per foot for gray cast iron hexagonal bar at 7,200 kg/m³ (ASTM A48 Class 30 / ISO 185). Every figure is for the section as drawn. A 6 m length of this size weighs 21.5 kg (48.3 lb per 20 ft).
At the reference dimensions (AF = 24 mm) this section has a cross-sectional area of 498.8 mm², giving 3.592 kg/m (2.413 lb/ft). Against carbon steel's 7,850 kg/m³ that is -8.3 % — the same section in steel would be 3.916 kg/m.
Hexagonal Bar — formula and derivation
Area of a hexagonal bar
A = (√3/2) · AF² ≈ 0.8660 · AF²
A = (√3/2) × AF², where AF is the distance across flats (the wrench size), not across corners
Worked through with the default dimensions:
A = (√3/2) × AF²A = 0.866025 × 24²A = 0.866025 × 576.0A = 498.8 mm²
- AF
- Across flats (AF) — Distance between opposite flats — the size a spanner grips. Hex bar is ordered by AF, not by corner-to-corner.
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 7,200 kg/m³ that is 3.5916 kg/m for the reference size above.
Cast iron hexagonal bar — size series
| Across flats (AF) | Cross-section | Mass / length |
|---|---|---|
| 5.0 mm | 21.65 mm² · 0.0336 in² | 0.156 kg/m · 0.105 lb/ft |
| 6.0 mm | 31.18 mm² · 0.0483 in² | 0.224 kg/m · 0.151 lb/ft |
| 8.0 mm | 55.43 mm² · 0.0859 in² | 0.399 kg/m · 0.268 lb/ft |
| 10 mm | 86.60 mm² · 0.1342 in² | 0.624 kg/m · 0.419 lb/ft |
| 12 mm | 124.71 mm² · 0.1933 in² | 0.898 kg/m · 0.603 lb/ft |
| 14 mm | 169.74 mm² · 0.2631 in² | 1.222 kg/m · 0.821 lb/ft |
| 17 mm | 250.28 mm² · 0.3879 in² | 1.802 kg/m · 1.211 lb/ft |
| 19 mm | 312.64 mm² · 0.4846 in² | 2.251 kg/m · 1.513 lb/ft |
| 22 mm | 419.16 mm² · 0.6497 in² | 3.018 kg/m · 2.028 lb/ft |
| 24 mm | 498.83 mm² · 0.7732 in² | 3.592 kg/m · 2.413 lb/ft |
| 27 mm | 631.33 mm² · 0.9786 in² | 4.546 kg/m · 3.054 lb/ft |
| 32 mm | 886.81 mm² · 1.3746 in² | 6.385 kg/m · 4.291 lb/ft |
| 36 mm | 1,122.37 mm² · 1.7397 in² | 8.081 kg/m · 5.430 lb/ft |
| 41 mm | 1,455.79 mm² · 2.2565 in² | 10.482 kg/m · 7.043 lb/ft |
| 46 mm | 1,832.51 mm² · 2.8404 in² | 13.194 kg/m · 8.866 lb/ft |
| 50 mm | 2,165.06 mm² · 3.3559 in² | 15.588 kg/m · 10.475 lb/ft |
Computed for Cast iron at 7200 kg/m³ (0.2601 lb/in³). ASTM A48 Class 30 / ISO 185.
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
Hexagonal 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 | 34.92 mm² · 0.0541 in² | 0.251 kg/m · 0.169 lb/ft |
| 5/16 in | 7.94 | 54.56 mm² · 0.0846 in² | 0.393 kg/m · 0.264 lb/ft |
| 3/8 in | 9.52 | 78.57 mm² · 0.1218 in² | 0.566 kg/m · 0.380 lb/ft |
| 7/16 in | 11.11 | 106.94 mm² · 0.1658 in² | 0.770 kg/m · 0.517 lb/ft |
| 1/2 in | 12.70 | 139.68 mm² · 0.2165 in² | 1.006 kg/m · 0.676 lb/ft |
| 9/16 in | 14.29 | 176.78 mm² · 0.2740 in² | 1.273 kg/m · 0.855 lb/ft |
| 5/8 in | 15.88 | 218.25 mm² · 0.3383 in² | 1.571 kg/m · 1.056 lb/ft |
| 3/4 in | 19.05 | 314.28 mm² · 0.4871 in² | 2.263 kg/m · 1.521 lb/ft |
| 7/8 in | 22.22 | 427.77 mm² · 0.6631 in² | 3.080 kg/m · 2.070 lb/ft |
| 1 in | 25.40 | 558.72 mm² · 0.8660 in² | 4.023 kg/m · 2.703 lb/ft |
| 1-1/4 in | 31.75 | 873.01 mm² · 1.3532 in² | 6.286 kg/m · 4.224 lb/ft |
| 1-1/2 in | 38.10 | 1,257.13 mm² · 1.9486 in² | 9.051 kg/m · 6.082 lb/ft |
| 2 in | 50.80 | 2,234.90 mm² · 3.4641 in² | 16.091 kg/m · 10.813 lb/ft |
Stock sizes in inches, converted exactly at 25.4 mm per inch. Material: Gray Cast Iron at 7200 kg/m³.
The same hexagonal bar in every material
Geometry is fixed and only density changes, so this table is the whole material-selection question in one view. Gray Cast Iron 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 | 3.916 | 2.631 | +0.0 % |
| Stainless Steel 304 | 8,000 | 0.2890 | 3.991 | 2.682 | +1.9 % |
| Stainless Steel 316 | 8,000 | 0.2890 | 3.991 | 2.682 | +1.9 % |
| Stainless Steel 316L | 8,000 | 0.2890 | 3.991 | 2.682 | +1.9 % |
| Stainless Steel 430 | 7,700 | 0.2782 | 3.841 | 2.581 | -1.9 % |
| Aluminum 6061-T6 | 2,700 | 0.0975 | 1.347 | 0.905 | -65.6 % |
| Aluminum 5052-H32 | 2,680 | 0.0968 | 1.337 | 0.898 | -65.9 % |
| Aluminum 7075-T6 | 2,810 | 0.1015 | 1.402 | 0.942 | -64.2 % |
| Copper C11000 | 8,940 | 0.3230 | 4.460 | 2.997 | +13.9 % |
| Brass C36000 | 8,500 | 0.3071 | 4.240 | 2.849 | +8.3 % |
| Bronze C93200 | 8,800 | 0.3179 | 4.390 | 2.950 | +12.1 % |
| Titanium Grade 2 | 4,510 | 0.1629 | 2.250 | 1.512 | -42.5 % |
| Gray Cast Iron | 7,200 | 0.2601 | 3.592 | 2.413 | -8.3 % |
| Lead | 11,340 | 0.4097 | 5.657 | 3.801 | +44.5 % |
| Rigid PVC (Type I) | 1,400 | 0.0506 | 0.698 | 0.469 | -82.2 % |
| HDPE (PE 100) | 960 | 0.0347 | 0.479 | 0.322 | -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 gray cast iron
The only common ferrous material lighter than steel, because the graphite flakes that give cast iron its damping and machinability also displace iron — 7,200 kg/m³ against steel’s 7,850, an 8.3 % saving. Those flakes are also why it fails in tension but excels in compression, and why engine blocks, machine bases and drainage products are cast iron. Normal spread is 7,150–7,350 kg/m³, so a large casting should always be weighed against the foundry’s own figure.
- Density
- 7,200 kg/m³ = 0.2601 lb/in³ · 0.9172× carbon steel · typical spread ±3 %
- Specification
- ASTM A48 Class 30 / ISO 185
- Equivalents
- EN GJL-250 · JIS FC250 · GB HT250
- Typical uses
- Machine tool bases · Engine blocks and manifolds · Drainage and soil pipe · Column and bracket castings
Density varies with graphite content and section thickness — thin sections cool faster and can differ from a heavy boss in the same casting.
About hexagonal bar
Hex bar is the one shape where the ordering dimension is not the dimension the formula wants. Stock is sold by across-flats (AF) because that is what the wrench grips, but the area formula needs AF as well — and the two are easy to confuse once a drawing quotes across-corners instead. Across-corners is a factor of 2/√3 (1.1547) larger than AF, so mixing them up inflates the calculated weight by 33 %. Always check which one the drawing calls out.
Specified by across-flats. Say so explicitly on the order — "across corners" gives a different bar.
Download this data
Cast iron hexagonal 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 gray cast iron hexagonal bar weigh?
At the reference dimensions (AF = 24 mm) a gray cast iron hexagonal bar of this size weighs 3.592 kg/m, or 2.413 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 hexagonal bar calculated?
Weight is cross-sectional area × length × density. For this shape the area is A = (√3/2) · AF² ≈ 0.8660 · AF². At the reference dimensions that gives 498.8 mm², and multiplying by gray cast iron's density of 7,200 kg/m³ gives 3.592 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 gray cast iron weigh more or less than steel?
It is lighter than carbon steel for the same section — about 8 % lighter at 7,200 kg/m³. Density is the only variable: the cross-sectional area depends purely on geometry, so a hexagonal 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 0.9172× carbon steel.
What is the cross-sectional area of a hexagonal 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 498.8 mm² (0.7732 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 cast iron hexagonal bar weigh the same as a cast iron 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.
Should I use Cast iron weight or carbon steel weight for costing?
Use the material you are actually buying. At 7,200 kg/m³ against carbon steel's 7,850 kg/m³, the same hexagonal bar differs by 8.3 % in mass. On a per-metre quote that is invisible; on a fabricated tonnage it is the difference between a margin and a loss. This page computes the steel figure as 3.916 kg/m for comparison.
Other materials, same hexagonal bar
The same geometry in every material, so the only variable is density.
- Carbon steel hexagonal bar — 7850 kg/m³
- SS 304 hexagonal bar — 8000 kg/m³
- SS 316 hexagonal bar — 8000 kg/m³
- AL 6061 hexagonal bar — 2700 kg/m³
- Copper hexagonal bar — 8940 kg/m³
- Brass hexagonal bar — 8500 kg/m³
- HDPE hexagonal bar — 960 kg/m³
- PVC hexagonal bar — 1400 kg/m³
Other Cast iron sections
The same density applied to every shape the site covers.
- Cast iron round bar — A = π/4 · d²
- Cast iron square bar — A = a²
- Cast iron flat bar — A = w · t
- Cast iron plate — A = w · t
- Cast iron round tube — A = π/4 · (D² − d²), d = D − 2t
- Cast iron 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
Hexagonal Bar area from A = (√3/2) · AF² ≈ 0.8660 · AF². Mass computed as area × length × density at 7,200 kg/m³ (ASTM A48 Class 30 / ISO 185). 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.