Round, Square and Hexagon Bar Sections: Mass of 1 m and Sizes

Round, square and hexagon bar: sizes and mass of 1 m

Round bar is graded by diameter, square bar by side, and hexagon bar by the distance between opposite flats. That distance is the across-flats size, the one a spanner fits. The distance between opposite corners of a hexagon is larger and is not in the tables.

The tables are calculated from nominal sizes for a steel density of 7850 kg/m³. Each kind of bar has its own table below.

Hot-rolled steel round bar · ГОСТ 2590-88

Diameter in millimetres; A is the section area in cm²; the mass of 1 m is in kilograms; the last column shows how many metres of bar make one tonne. Round bar to GOST 2590-88.

Hot-rolled steel square bar · ГОСТ 2591-88

Side in millimetres; A is the section area in cm²; the mass of 1 m is in kilograms; the last column is metres per tonne. Square bar to GOST 2591-88.

Hot-rolled steel hexagon bar · ГОСТ 2879-88

Across-flats size in millimetres; A is the section area in cm²; the mass of 1 m is in kilograms; the last column is metres per tonne. Hexagon bar to GOST 2879-88.

How the section area is worked out

The area of a round bar is πd²/4, where d is the diameter. For a square bar it is a², where a is the side. For a hexagon bar the area is (√3/2)·s², where s is the across-flats size.

The mass of 1 m is the area times the density of steel. A 20 mm round bar has an area of 3.14 cm² and a mass of 2.466 kg/m. A 20 mm square bar has 4 cm² and 3.14 kg/m. A hexagon bar of 20 mm across flats has 3.46 cm² and 2.719 kg/m.

How much heavier square bar is than round bar

A square bar whose side equals the diameter of a round bar is heavier by a factor of 4/π, about 1.27. It follows from the formulas: the square area is a², the round area is πa²/4. For the 20 mm size it is 3.14 kg/m against 2.466 kg/m.

A hexagon bar of 20 mm across flats is about 10% heavier than a 20 mm round bar: 2.719 kg/m against 2.466 kg/m. So an order has to give the size together with the shape: round Ø20, square 20 and hexagon 20 are three different masses.

How to get the mass of a blank from the table

The mass of a blank is its mass per metre times its length. Three metres of Ø20 round bar weigh 7.4 kg (2.466 × 3), and a 6 m length of the same bar weighs 14.8 kg. A tonne of Ø20 round bar is 405 m long.

Large sections give few metres per tonne: Ø100 round bar weighs 61.65 kg/m, so a tonne is only 16.2 m. A 50 mm square bar gives 19.62 kg/m and 51 m per tonne.

When several items have to be weighed at once, use the calculator: it takes its sizes from the same tables.

Where round, square and hexagon bar are used

Round bar is stock for shafts, axles, pins and bushings turned on a lathe, and also for rods, bars and ties. Square bar goes into grilles, fences, forging and parts that need flat faces. Hexagon bar is stock for nuts, bolts, fittings and parts meant for a spanner.

In steel structures round and square bars are most often needed as ties, bracing and fence elements. The section is chosen by calculation.

Calculator and ordering

The weight of round, square or hexagon bar of any length can be worked out in the rolled metal calculator. The other kinds of rolled metal with their masses and sizes are in the rolled metal handbook.

Bars, ties or blanks for a structure can be ordered together with the product: the POLYGONAL company makes steel structures to the customer’s drawings, prepares KM and KMD drawings and galvanizes the products (hot-dip galvanizing).