Round Bar Weight Calculator
Enter the diameter and length of a solid round bar to get its weight in kg or lb, plus the weight per metre or foot.
The round bar weight calculator works out the weight of a solid round bar from its diameter, length, number of pieces and material. It runs in your browser, is free, and needs no sign-up. The tool opens on round bar in mild steel, and it uses the same weight engine as the metal weight, steel plate, pipe and steel beam pages.
You can pick mild or carbon steel, stainless steel 304 or 316, aluminum, copper, brass, bronze, titanium and several other metals, or enter a custom density for anything else. Results show the weight of one piece, the total weight, the weight per length, and the calculation steps. Use it as a fast way to calculate round bar weight for quotes, orders and planning, whether you need a steel bar weight calculator, an aluminum round bar weight calculator, or a stainless steel round bar weight calculator.
At a glance
Round Bar Weight Calculator is a free browser tool that works out the weight of a solid round bar from its diameter, length, number of pieces and material, in kg or lb.
- Free, runs in the browser, and needs no sign-up.
- Steel density used is 7.85 g/cm³, which is 7,850 kg/m³.
- Formula: weight = π/4 × d² × length × density, with consistent units.
- Materials include mild steel, stainless 304 and 316, aluminum, copper, brass, bronze and titanium, or a custom density.
- Example: a 25 mm steel bar, 6 m long, weighs 23.12 kg.
- Results are estimates from nominal size and standard density, so verify critical designs against the applicable standard.
Sources: Density (Wikipedia) (checked 2026-10-15) · Material density chart (AIMS Industrial) (checked 2026-10-15)
How to use the round bar weight calculator
- At the top of the tool, choose Metric (mm) or Imperial (in).
- Check that the Shape list is set to Round bar.
- Open the material list and pick a material, such as Mild / carbon steel, Stainless steel 304 or Aluminum 6061. For anything not on the list, choose Custom density and type the density.
- Enter the Diameter in mm or in.
- Enter the Length of one piece in metres or feet.
- Enter the Number of pieces. The Total weight result appears when this is more than 1.
- If you need a material cost, open More options and enter a price in Price per kg (metric) or Price per lb (imperial).
- Read the results: weight of one piece, total weight, weight per length, cross-section area, volume of one piece and density used. Check the cross-section sketch and the calculation steps, which show the formula with your own numbers filled in, line by line.
Under the result, Print / save result prints your inputs, results, steps and the date. Use your browser’s Save as PDF option to keep a PDF. Copy link creates a link that reopens the page with the same inputs, and Reset clears the form.
How to calculate the weight of a steel bar
Multiply the bar’s cross-section area by its length, then by the density of the steel. Steel is 7.85 g/cm³, which is 7,850 kg/m³. The bar’s cross-section is a circle, so its area comes from the diameter.
Formula of weight of steel bar
The weight of a round bar is:
weight = π/4 × d² × length × density
Use consistent units. If the diameter and length are in metres and the density is in kg/m³, the result is in kilograms. A 25 mm steel bar 6 m long has a cross-section of about 490.9 mm², which gives 23.12 kg. To use another metal, change only the density. Stainless 304 is about 1.02 times the weight of mild steel for the same size, brass is about 1.08, copper is about 1.14, and aluminum 6061 is about 0.34.
Weight of steel bar per meter formula
For steel round bar, weight per metre in kilograms equals the diameter in millimetres squared multiplied by 0.006165. Written another way, that is d²/162.2. A 20 mm bar therefore weighs 400 × 0.006165 = 2.466 kg per metre.
Because weight depends on the square of the diameter, doubling the diameter quadruples the weight. In imperial units, a 1 in steel bar weighs 2.673 lb per foot, and a 5/8 in bar weighs 1.044 lb per foot.
Steel rebar weight per meter
Reinforcing bar, or rebar, is sold by its nominal diameter. Its weight per metre is therefore the round-bar weight for that diameter. A 12 mm bar weighs 0.888 kg per metre, a 16 mm bar weighs 1.578 kg per metre, and a 20 mm bar weighs 2.466 kg per metre.
US bar sizes follow the same logic. A #4 (1/2 in) bar weighs 0.668 lb per foot, a #5 (5/8 in) bar weighs 1.043 lb per foot, and a #8 (1 in) bar weighs 2.670 lb per foot. These match the standard ASTM bar sizes.
Round bar weight chart
Weight per metre of solid round bar, from the tool (density: steel 7.85, aluminum 6061 2.70, stainless 304 8.00 g/cm³):
| Diameter | Steel kg/m | Aluminum 6061 kg/m | Stainless 304 kg/m |
|---|---|---|---|
| 6 mm | 0.222 | 0.076 | 0.226 |
| 8 mm | 0.395 | 0.136 | 0.402 |
| 10 mm | 0.617 | 0.212 | 0.628 |
| 12 mm | 0.888 | 0.305 | 0.905 |
| 16 mm | 1.578 | 0.543 | 1.608 |
| 20 mm | 2.466 | 0.848 | 2.513 |
| 25 mm | 3.853 | 1.325 | 3.927 |
| 32 mm | 6.313 | 2.171 | 6.434 |
| 40 mm | 9.865 | 3.393 | 10.053 |
| 50 mm | 15.413 | 5.301 | 15.708 |
Reinforcing bar in US sizes uses the same formula at the nominal diameter. The tool’s value next to the weight in the ASTM size table:
| US bar size | Nominal diameter | Tool, lb/ft | ASTM size table, lb/ft |
|---|---|---|---|
| #3 | 3/8 in | 0.376 | 0.376 |
| #4 | 1/2 in | 0.668 | 0.668 |
| #5 | 5/8 in | 1.044 | 1.043 |
| #6 | 3/4 in | 1.503 | 1.502 |
| #7 | 7/8 in | 2.046 | 2.044 |
| #8 | 1 in | 2.673 | 2.670 |
The small differences come from rounding in the published table.
Sources
Data and rules used by this tool (checked October 2026):
Frequently asked questions
What is the weight of a 25 mm steel bar per metre?
A 25 mm steel round bar weighs 3.853 kg per metre. A 6 m piece weighs 23.12 kg.
Can I use this calculator for stainless steel round bar?
Yes. Choose Stainless steel 304 or 316, which uses a density of 8.00 g/cm³. For example, a 30 mm stainless 304 bar 2 m long weighs 11.31 kg.
Can I calculate the weight of a plastic round bar?
Yes. Choose Custom density and type the density of the plastic. The tool does not list plastic densities, so use the figure from your supplier’s data sheet.
Why does my supplier’s weight differ from the result?
The calculator gives an estimate based on nominal size and a standard density. Actual bars can vary slightly in diameter and alloy, so verify critical designs against the applicable standard.
Does the calculator work for square or hex bar?
Yes. Change the Shape list to Square bar, Flat bar or Hex bar. This page opens on Round bar.
Can I use the results in paid work?
Yes. Results and files can be used in quotes, client jobs and products you sell, royalty-free, with no attribution required. The only limit is that you may not copy the site itself as a competing service.
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