Metal weight calculator
Weight of a section
- Weight per metre
- 2.48 kg
- Weight per piece
- 14.9 kg
- Total
- 14.9 kg
- Pieces per tonne
- 67
- Density
- 7.90 g/cm³
Root fillets and toe radii are not in the formula, so an open section reads under the rolled weight: 1.3 to 2.8 percent for an equal angle, and a similar margin for unequal angles, channels and T-profiles.
How the calculation works
Steel section weight is the product of cross-sectional area and density. With dimensions in millimetres and density in grams per cubic centimetre, area in square millimetres multiplied by density and divided by 1,000 gives kilograms per metre. The calculation does not use a measured or weighed value. It gives the weight of a section rolled exactly to nominal size.
| Section | Cross-sectional area (mm²) | Dimensions in mm |
|---|---|---|
| Round bar | π × d² ÷ 4 | d = diameter |
| Square bar | a² | a = side |
| Hexagon bar | (√3 ÷ 2) × a² | a = across flats |
| Flat bar | w × t | w = width, t = thickness |
| Equal angle | 2 × A × t − t² | A = leg, t = thickness |
| Unequal angle | (A + B − t) × t | A, B = legs, t = thickness |
| Channel | tw × (h − 2tf) + 2 × b × tf | h = depth, b = flange width, tw = web thickness, tf = flange thickness |
| T-profile | b × t + (h − t) × t | b = flange width, h = depth, t = thickness |
| Pipe or tube | π × (OD − t) × t | OD = outside diameter, t = wall |
These are the standard section formulas printed in steel weight charts: each open section is treated as the rectangles that compose it, with the overlap counted once. Root fillets and toe radii are excluded, so a rolled angle, channel or T-profile weighs slightly more than the calculated figure; for an equal angle the difference against the published tables is 1.3 to 2.8 percent.
The sections cover the full Laxcon catalogue of calculable profiles: round covers hot rolled, bright, peeled and precision shaft quality bar; square, hexagon and flat cover the bright and cold-drawn sections; the angle, channel and T-profile sections cover the HRAP range; pipe covers seamless pipe and hollows. A round cornered square is calculated as a square bar, from which the radiused corners subtract slightly. Forging quality ingots are quoted by piece weight, and threaded bars per size from the thread standards, so neither is calculated from a section.
The weight chart page is a tabulation of the same rules in reverse form. It gives a single multiplier per section at 7.90 g/cm³ for faster manual calculation.
A worked example
A 20 mm round bar in 304 provides an example of the calculation. The area is π × 20² ÷ 4, which is 314 mm². At 7.90 g/cm³, the weight is 314 × 7.90 ÷ 1,000, or 2.48 kg per metre. A 6 metre bar therefore weighs 14.9 kg. One tonne contains 67 bars of that size. At a length of 3 metres, the piece weight is 7.4 kg, while the weight per metre remains unchanged. Length scales the piece weight but not the section weight per metre.
Round bar weight, 5 mm to 100 mm
The listed values are calculated at 7.90 g/cm³. Piece weights and counts per tonne use a 6 metre length. A 20 mm bar at 2.48 kg per metre weighs 14.9 kg per length, and 67 lengths make a tonne.
| Diameter (mm) | Weight (kg/m) | Weight per 6 m length (kg) | Lengths per tonne |
|---|---|---|---|
| 5 | 0.16 | 0.9 | 1,074 |
| 6 | 0.22 | 1.3 | 746 |
| 8 | 0.40 | 2.4 | 420 |
| 10 | 0.62 | 3.7 | 269 |
| 12 | 0.89 | 5.4 | 187 |
| 14 | 1.22 | 7.3 | 137 |
| 16 | 1.59 | 9.5 | 105 |
| 18 | 2.01 | 12.1 | 83 |
| 20 | 2.48 | 14.9 | 67 |
| 22 | 3.00 | 18.0 | 55 |
| 25 | 3.88 | 23.3 | 43 |
| 28 | 4.86 | 29.2 | 34 |
| 30 | 5.58 | 33.5 | 30 |
| 32 | 6.35 | 38.1 | 26 |
| 35 | 7.60 | 45.6 | 22 |
| 38 | 8.96 | 53.8 | 19 |
| 40 | 9.93 | 59.6 | 17 |
| 45 | 12.56 | 75.4 | 13 |
| 50 | 15.51 | 93.1 | 11 |
| 55 | 18.77 | 112.6 | 9 |
| 60 | 22.34 | 134.0 | 7 |
| 65 | 26.21 | 157.3 | 6 |
| 70 | 30.40 | 182.4 | 5 |
| 75 | 34.90 | 209.4 | 5 |
| 80 | 39.71 | 238.3 | 4 |
| 85 | 44.83 | 269.0 | 4 |
| 90 | 50.26 | 301.5 | 3 |
| 95 | 56.00 | 336.0 | 3 |
| 100 | 62.05 | 372.3 | 3 |
An 8 mm rod is a round section with a weight of 0.40 kg per metre and 2.4 kg per 6 metre length. This is the size asked about most often. Laxcon cold finishes bright bars from 5 mm to 115 mm and rolls hot rolled round bars from 16 mm to 125 mm.
Square and hexagon bar weight
The square and hexagon bar values are weight calculations based on side length and size across flats, respectively, at 7.90 g/cm³. A hexagon weighs 86.6 percent of a square with the same size. Its area is (√3 ÷ 2) × a², compared with a² for the square.
| Size (mm) | Square bar (kg/m) | Hexagon bar (kg/m) |
|---|---|---|
| 12 | 1.14 | 0.99 |
| 14 | 1.55 | 1.34 |
| 16 | 2.02 | 1.75 |
| 18 | 2.56 | 2.22 |
| 20 | 3.16 | 2.74 |
| 22 | 3.82 | 3.31 |
| 25 | 4.94 | 4.28 |
| 28 | 6.19 | 5.36 |
| 30 | 7.11 | 6.16 |
| 32 | 8.09 | 7.01 |
| 35 | 9.68 | 8.38 |
| 40 | 12.64 | 10.95 |
| 45 | 16.00 | 13.85 |
| 50 | 19.75 | 17.10 |
| 55 | 23.90 | 20.70 |
Pipe and tube weight
A pipe cross-section is an annulus. Its area is π × (OD − t) × t, which is the mean diameter multiplied by the wall thickness. This formula is exact rather than approximate. A pipe with a 60.3 mm outside diameter and a 3.91 mm wall has a section of 692 mm² and weighs 5.47 kg per metre at 7.90 g/cm³. The table below applies the same rule to the schedule 40S walls of ASME B36.19M.
| Nominal bore (mm) | Outside diameter (mm) | Wall, schedule 40S (mm) | Weight (kg/m) |
|---|---|---|---|
| 15 | 21.3 | 2.77 | 1.27 |
| 20 | 26.7 | 2.87 | 1.70 |
| 25 | 33.4 | 3.38 | 2.52 |
| 32 | 42.2 | 3.56 | 3.41 |
| 40 | 48.3 | 3.68 | 4.08 |
| 50 | 60.3 | 3.91 | 5.47 |
Published schedule tables are weight tables calculated at 7.85 g/cm³, the carbon steel figure. Their weights are about 0.6 percent below the values in this column. The seamless pipe and mother hollow page lists the size, schedule and tolerance.
Why the density changes with the grade
Density is the only non-dimensional variable in the calculation. Its value varies with the alloy. Nickel and molybdenum are heavier than the iron they replace. A molybdenum-bearing austenitic grade such as 316 is therefore denser than 304. Ferritic and martensitic grades contain little or no nickel and are the lightest stainless families. The density range is about four percent. This difference equals one tonne for a 25 tonne shipment.
| Family or grade | Density (g/cm³) | Basis |
|---|---|---|
| Austenitic chromium nickel, 304 and 321 | 7.90 | EN 10088-1 nominal, 1.4301 and 1.4541 |
| Austenitic chromium nickel molybdenum, 316 | 8.00 | EN 10088-1 nominal, 1.4401 and 1.4404 |
| Duplex, 2205 | 7.80 | EN 10088-1 nominal, 1.4462 |
| Ferritic, 409 and 430 | 7.70 | EN 10088-1 nominal, 1.4016 |
| Martensitic, 410 and 420 | 7.75 | Mill data sheets, 1.4006 and 1.4021 |
| AISI 304 and 304L | 7.93 | Grade data sheet |
| AISI 316 and 316L | 7.98 | Grade data sheet |
| Carbon and alloy steel | 7.85 | Pipe schedule and structural section tables |
The two density bases are separate reference systems. EN 10088-1 publishes one rounded figure per family. European section and pipe tables use this basis. Individual grade data sheets publish a measured figure for each specific alloy. These data sheets give 7.93 for 304 and 7.98 for 316. Stockist sheets place the ferritic and martensitic grades between 7.70 and 7.75. The difference between the two bases is under half a percent and is well within rolling tolerance. A quotation should state one basis and apply it consistently.
The grades pages are listings of composition by grade. The grade equivalents page lists the equivalent designations.