Steel Weight Calculator

1. Choose the shape and the material.
2. Enter the dimensions in millimetres and the length in metres. Flat bars also need a thickness.
3. Set the quantity and read the weight per piece, per metre and in total, all updating live.

Each output helps you order and plan:

The weight of a metal bar depends on just two things: how much space it takes up, its volume, and how heavy the material is per unit of volume, its density. A thicker or longer bar has more volume, and a denser metal weighs more for the same size. Everything else follows from those two facts.

Density is why the same shape in different metals weighs so differently. Mild steel is about 7,850 kilograms per cubic metre, stainless a little more, while aluminium is under a third of that. Choosing the material is therefore as important as the dimensions.

It finds the cross-section area from the shape, multiplies by the length for volume, then by the density for weight.

For a round bar the area is pi * (d/2)^2, for a square bar it is the side squared, and for a flat bar it is width times thickness. The area in square millimetres is converted to square metres, multiplied by the length in metres for the volume, and then by the density to give the weight in kilograms.

1. Work out the cross-section area from the shape and dimensions.
2. Multiply by the length for the volume.
3. Multiply by the material density for the weight.

The per-metre figure is simply the area times the density, independent of the length you enter.

Take a 12 millimetre round mild steel bar. Its area is pi * 6^2 = 113.1 square millimetres, which is 0.0001131 square metres. Multiplying by the density of 7,850 gives about 0.888 kilograms per metre.

A 6 metre length therefore weighs about 5.33 kilograms, and ten of them come to roughly 53.3 kilograms, useful when planning a delivery or a lift.

Switch the material to aluminium and the same bar drops to about 0.306 kilograms per metre, showing how much lighter it is than steel for an identical shape.

The density sets the weight for any given shape; these are common values.

Aluminium is roughly a third the weight of steel for the same shape, which is why it is chosen where weight matters. To convert dimensions between units first, the length converter helps.

The theoretical weight follows the formula, but real bars vary around it.

Dimensions

Weight rises with the square of a round bar diameter, so a small increase in thickness adds a lot of mass.

Material

Density varies by metal and alloy, so the same shape can weigh very differently depending on what it is made of.

Manufacturing Tolerance

Bars are made to a tolerance, so a real piece can be slightly heavier or lighter than the nominal calculation.

Coatings and Finish

Galvanising, paint or plating add a little weight beyond the base metal.

Estimating Material Cost

Steel is often priced by weight, so the per-metre figure turns a length into a cost.

Planning Transport and Lifting

Knowing the total weight helps you choose the right vehicle, crane or number of hands.

Structural Checks

Dead-load estimates for a frame start with the weight of its members.

1. Mixing Millimetres and Metres

Enter the cross-section in millimetres and the length in metres, as the calculator expects.

2. Forgetting the Thickness on a Flat Bar

A flat bar needs both width and thickness; a round or square bar needs only one dimension.

3. Using the Wrong Density

Aluminium, brass and steel differ greatly. Pick the correct material.

4. Ignoring Tolerance for Critical Work

The result is nominal. For load-bearing or precise orders, use certified data.

5. Squaring the Radius Wrongly

For a round bar, use half the diameter as the radius before squaring it.

The math is exact for the nominal dimensions and standard densities, but real material carries tolerances.

Find the cross-section area, multiply by the length for volume, then by the density. For a 12 mm round steel bar that is about 0.888 kilograms per metre.

A 12 millimetre round mild steel bar weighs about 0.888 kilograms per metre, so a 6 metre length is roughly 5.33 kilograms.

Mild steel is about 7,850 kilograms per cubic metre. Stainless steel is a little higher at around 8,000, while aluminium is about 2,700.

Choose the flat bar or plate option, enter the width and thickness in millimetres and the length in metres, and the calculator returns the weight.

Yes, through the cross-section area. A round bar uses pi times the radius squared, a square bar the side squared, and a flat bar width times thickness.

Because its density is about a third of steel. The same shape in aluminium weighs roughly a third as much, which is why it is used where weight matters.

It is a theoretical weight from nominal dimensions. Real bars vary within a tolerance, and coatings add a little, so treat it as a close estimate.

Multiply the cross-section area in square metres by the density. It does not depend on the length, so it stays the same for any piece of that bar.

No. The calculation runs in your browser, and nothing you enter is sent anywhere unless you Save a result, which stays on this device only.

• Density (Wikipedia).
• Steel (Wikipedia).
• Volume of a cylinder (Wikipedia).