CNC machining
Milling, turning, 3- to 5-axis machining centres
Free calculator
Raw part mass calculation
Choose the shape and material and enter the dimensions in millimetres: the volume, unit mass and total mass are displayed in grams and kilograms.
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- Calculated in your browser
- Formulas and tables shown
Raw part mass calculator
Unit mass · plate or sheet
5.8875 kg
i.e. 5,887.5 g
Total mass · 1 part
5.8875 kg
i.e. 5,887.5 g
Volume
750 cm³
750,000 mm³
Density
7.85 g/cm³
Carbon or alloy steel
The calculation is done in your browser: the values you enter are neither sent nor saved.
Typical densities
Typical values, to be checked against the grade. The material selected in the calculator is highlighted.
| Material | g/cm³ | kg/m³ | Note |
|---|---|---|---|
| Steels and cast irons | |||
| Carbon or alloy steel | 7.85 | 7,850 | S235, S355, C45, 42CrMo4… |
| Grey cast iron | 7.20 | 7,200 | EN-GJL: approximately 7.1 to 7.3 |
| Stainless steel | |||
| Stainless steel 304 (1.4301) | 7.93 | 7,930 | Austenitic, the most common |
| Stainless steel 316L (1.4404) | 7.98 | 7,980 | Austenitic with molybdenum |
| Aluminium | |||
| Aluminium 5083 | 2.66 | 2,660 | Al-Mg, sheets and plates |
| Aluminium 6061 | 2.70 | 2,700 | Al-Mg-Si, machining and profiles |
| Aluminium 7075 | 2.81 | 2,810 | Al-Zn, high strength |
| Copper alloys | |||
| Brass | 8.50 | 8,500 | From 8.4 to 8.7 depending on zinc content |
| Copper | 8.90 | 8,900 | Cu-ETP; 8.96 for pure copper |
| Bronze (tin) | 8.80 | 8,800 | CuSn8, CuSn12…; other bronzes differ |
| Titanium | |||
| Titanium Ti-6Al-4V (grade 5) | 4.43 | 4,430 | The most common titanium alloy |
| Engineering plastics | |||
| POM (polyacetal) | 1.41 | 1,410 | Unfilled copolymer |
| PA6 (polyamide 6) | 1.14 | 1,140 | Unfilled; glass fibre makes it heavier |
| PEEK | 1.30 | 1,300 | Unfilled |
| ABS | 1.05 | 1,050 | Approximately 1.03 to 1.06 |
| HDPE (high-density polyethylene) | 0.95 | 950 | Approximately 0.94 to 0.97 |
| PMMA (acrylic) | 1.18 | 1,180 | Perspex, Plexiglas… |
How to read the result
The calculator gives the volume of the raw stock, then its mass: mass = volume × density. The dimensions to enter are those of the raw stock, that is, the sheet, bar or tube before machining, not those of the finished part. The result is therefore the mass of material to be sourced. It is used to estimate the cost of the material, the weight of a package, the capacity of lifting equipment or the machine suited to the part.
The mass of the finished part is lower: machining turns part of the raw stock into chips, sometimes more than half for a heavily hollowed part. For the mass of a finished part with a complex shape, use the volume calculated by your CAD software instead and multiply it by the same density.
Results are given in grams and kilograms, and the volume in cm³ and mm³ so that you can cross-check it. A cubic centimetre of material with density ρ (in g/cm³) weighs ρ grams: 1 cm³ of steel weighs about 7.85 g. With the quantity, the calculator also gives the total mass of the batch.
The formulas used
All dimensions are entered in millimetres. The volume is calculated in mm³, converted to cm³ (1 cm³ = 1,000 mm³), then multiplied by the density in g/cm³ to obtain grams.
| Shape | Volume | Note |
|---|---|---|
| Plate or sheet | V = L × l × e | Length, width, thickness |
| Solid round bar | V = π × Ø² / 4 × L | Ø: diameter |
| Round tube | V = π × t × (Ø outer − t) × L | Equivalent to π / 4 × (Ø outer² − Ø inner²) × L, with Ø inner = Ø outer − 2t |
| Solid square or rectangular bar | V = a × b × L | A square is a rectangle where a = b |
| Square or rectangular tube | V = [a × b − (a − 2e) × (b − 2e)] × L | Sharp corners: outer fillets are ignored |
| Hexagon across flats | V = (√3 / 2) × s² × L ≈ 0,866 × s² × L | s: distance between two parallel faces |
A few useful equivalences: 1 g/cm³ = 1 kg/dm³ = 1,000 kg/m³, and 1 kg = 1,000 g. Mass in kilograms is not weight: the corresponding force is about 9.81 N per kilogram.
Pitfalls to avoid
- Density depends on the grade. The values in the table are typical values: an alloy steel, a leaded brass or a particular aluminium alloy may differ by a few per cent. For a contractual calculation (transport, permissible load), take the value from the material certificate or the supplier’s data sheet.
- Commercial stock and theoretical mass. Commercially available sheets, tubes and sections have thickness and shape tolerances: the actual mass differs from the theoretical mass by a few per cent.
- Square tubes have rounded corners. The sharp-corner calculation slightly overestimates the mass of a commercial tube.
- Machining allowance. Raw stock is ordered larger than the finished part, by a few millimetres per machined face: enter the dimension of the raw stock, not that on the drawing.
- Millimetres, not centimetres. All dimensions are entered in mm. Entering 5 for a thickness of 5 cm divides the mass by 10.
- Plastics vary with fillers and moisture. A glass fibre filler increases the density, and a PA6 that absorbs water gains a few per cent in mass.
In a drawing and in a request for quote
In a request, the unit mass helps workshops assess handling, transport and the machine to use: a 200 g part and a 40 kg part do not go through the same equipment. State it with the quantity, and specify the exact material and grade (“aluminium 6061-T6” rather than “alu”), because the grade determines the density, the machining behaviour and the material price.
To estimate the cost of the material, multiply the mass of the raw stock by the price per kilo quoted by your supplier: it varies widely with the grade, the format and market prices. The material price is only one part of the price of a machined part: programming, set-up and machining time, tooling, treatments and inspection also count. The guide on CNC machining prices details these items, and the one on materials for machined parts helps you choose the grade.
Frequently asked questions
A question not answered here? Visit the help centre or write to us.
How do I calculate the mass of a part?
Mass = volume × density. Calculate the volume of the shape (for example L × W × t for a plate), convert it to cm³ (1 cm³ = 1,000 mm³), then multiply by the density in g/cm³ to obtain grams. The calculator does this for six common stock shapes.
What is the density of steel, stainless steel and aluminium?
Typical values: about 7.85 g/cm³ for structural steel, 7.93 for 304 stainless, 7.98 for 316L, and from 2.66 to 2.81 depending on the aluminium alloy (2.70 for 6061). They vary slightly with the grade: check them on the material data sheet.
Does the calculation give the mass of the finished part?
No: it gives the mass of the raw stock at the dimensions entered. A machined part is lighter, because machining removes material. For a finished part with a complex shape, use the volume supplied by your CAD software and multiply it by the density.
How do I convert grams to kilograms?
Divide by 1,000: 1 kg = 1,000 g. The calculator displays both units. For density, 1 g/cm³ equals 1 kg/dm³ and 1,000 kg/m³.
Can I calculate the mass of a material that is not in the list?
Yes: choose “Custom density” in the materials list and enter the value in g/cm³, for example 2.2 for PTFE. You will find it on the material’s data sheet.
Related expertise
Workshops to manufacture, treat or inspect the part you are calculating.
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TIG, MIG, structures, tanks, metalwork
Guides to go further
Aluminium, stainless steel, steel, engineering plastics: choosing the right material for your parts
Aluminium 6082 or 7075, stainless 304L or 316L, POM or PA6: the criteria for choosing the right material, a comparison table and the effect of this choice on price and lead times.
CNC machining prices: how is a quote calculated?
Programming, setup, cycle time, material, finishing, inspection: what a CNC machining quote contains, why quantity changes everything and how to reduce the cost.
Laser cutting and sheet metal bending: prices, thicknesses and good practice
Choose the right cutting process, know the usual thicknesses, understand what drives the price of a sheet metal part and design parts that bend without extra cost.
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