Weight from dimensions for 21 metals and plastics — block, round bar, hex and tube. But a machined part has two weights that matter, and most calculators only give you one: the finished part, and the larger blank you actually pay for.
So this one also returns the buy-to-fly ratio, the material cost of the blank, what the same part weighs in every other grade, and the chargeable weight your airfreight will actually be billed on.
Built and maintained by EKINSUN, a custom parts manufacturer. We machine parts in every grade in this table. Send a STEP file or a PDF drawing if you have one — and if you do not, a dimensioned sketch, a photo with a caliper, or the worn part itself is equally fine. One piece for a prototype or a breakdown, or a blanket order with scheduled call-offs when the volume is real. Quote in 12 h.
// Shape · material · dimensions in mm
Enter the finished part's outside dimensions. The blank is worked out from these by adding a 3 mm machining allowance on every side.
Free, no sign-up, no CAD file needed — a sketch or a photo with a caliper is enough. MOQ 1, real quote within 12 h.
Your part weighs 89.1 g finished, but you buy 254.1 g of Aluminium 6061-T6 to make it — a buy-to-fly of 2.9 : 1, with 165.0 g leaving as swarf. We machine this from a sketch or a photo, no CAD file needed. Send what you have →
Ask a shop for a machined part and you are buying a piece of stock, not the shape you drew. The bar or plate has to be larger than the part in every direction so the cutter can clean up the sawn ends, get under the mill scale, take out any bow in the bar, and leave something for the vice to hold. About 3 mm per side covers it on ordinary work.
On a big part that allowance is a rounding error. On a small one it is most of the purchase. A 60 × 40 × 25 mm part carries a 66 × 46 × 31 mm blank — 57% more material than the finished envelope, before a single pocket has been cut. Then the pockets come out too, and what you paid for leaves in the swarf bin.
That is what buy-to-fly measures: kilograms bought per kilogram delivered. Nobody cares at 1.4 to 1 in aluminium. At 6 to 1 in titanium it is most of the quotation, and it is the number that should make you ask whether the part wants to be a smaller blank, a near-net casting, or a different shape entirely.
Weight is almost never the question on its own. The real question sitting behind it is whether this part should be made of something else — and that comparison needs weight and material cost side by side, not weight alone.
| Material | Density | Part weight | vs current | Blank material cost |
|---|---|---|---|---|
| Aluminium 6061-T6 | 2.70 | 89.1 g | — | €2.41 |
| Aluminium 7075-T6 | 2.81 | 92.7 g | +4% | €4.76 |
| Magnesium AZ31 | 1.77 | 58.4 g | -34% | €4.00 |
| Titanium Ti-6Al-4V | 4.43 | 146.2 g | +64% | €37.52 |
| Steel S235 / 1018 | 7.85 | 259.1 g | +191% | €3.32 |
| Steel 42CrMo4 / 4140 | 7.85 | 259.1 g | +191% | €5.54 |
| Cast iron GJL-250 | 7.20 | 237.6 g | +167% | €4.07 |
| Stainless 303 | 7.90 | 260.7 g | +193% | €8.92 |
| Stainless 304 | 8.00 | 264.0 g | +196% | €9.04 |
| Stainless 316L | 8.00 | 264.0 g | +196% | €12.05 |
| Brass CuZn39Pb3 / CW614N (US ≈ C360) | 8.47 | 279.5 g | +214% | €14.35 |
| Bronze CuSn8 | 8.80 | 290.4 g | +226% | €17.39 |
| Copper Cu-ETP | 8.96 | 295.7 g | +232% | €16.44 |
| Zinc ZAMAK 5 | 6.60 | 217.8 g | +144% | €5.28 |
| POM / Delrin | 1.41 | 46.5 g | -48% | €1.66 |
| Nylon PA6 | 1.14 | 37.6 g | -58% | €1.18 |
| PTFE | 2.17 | 71.6 g | -20% | €7.15 |
| PMMA (acrylic) | 1.18 | 38.9 g | -56% | €1.39 |
| ABS | 1.05 | 34.6 g | -61% | €0.99 |
| PC (polycarbonate) | 1.20 | 39.6 g | -56% | €1.58 |
| PEEK | 1.30 | 42.9 g | -52% | €24.47 |
Figures above are for the calculator's starting example — a 60 × 40 × 25 mm part with about half machined away. Change the inputs and every row recalculates for your own part.
One caution worth stating plainly, because it is the most common mistake made off the back of a weight table: aluminium 6061 is about 34% of the weight of steel, but also about a third of the stiffness. Swapping material while keeping every dimension identical gives you a part that flexes roughly three times as much. The usual right answer is to change material and add section where the load actually is, which still lands well under the steel weight. If you are not sure where that is, send us the part and what it does — that conversation is free and it is a better use of ten minutes than a spreadsheet.
Every figure is a standard published value for the grade, printed here so you can check the arithmetic rather than trust a black box. Stock prices are indicative small-quantity sawn-blank bands — what a supplier charges for a piece, not the tonnage commodity price — and they move with the metal market.
| Material | Density (g/cm³) | kg per dm³ | Stock price (€/kg) | Typical use |
|---|---|---|---|---|
| Aluminium 6061-T6 | 2.70 | 2.70 | 7 – 12 | Brackets, housings, general parts |
| Aluminium 7075-T6 | 2.81 | 2.81 | 14 – 22 | Higher strength structural parts |
| Magnesium AZ31 | 1.77 | 1.77 | 18 – 30 | Weight-critical, non-structural |
| Titanium Ti-6Al-4V | 4.43 | 4.43 | 60 – 120 | Aerospace, medical, marine |
| Steel S235 / 1018 | 7.85 | 7.85 | 3 – 6 | Weldments, low-cost mild steel |
| Steel 42CrMo4 / 4140 | 7.85 | 7.85 | 5 – 10 | Shafts, pins, loaded parts |
| Cast iron GJL-250 | 7.20 | 7.20 | 4 – 8 | Housings, damping, wear faces |
| Stainless 303 | 7.90 | 7.90 | 9 – 15 | Free-machining, non-welded |
| Stainless 304 | 8.00 | 8.00 | 9 – 15 | General corrosion resistance |
| Stainless 316L | 8.00 | 8.00 | 12 – 20 | Marine, chemical, medical |
| Brass CuZn39Pb3 / CW614N (US ≈ C360) | 8.47 | 8.47 | 14 – 22 | Fittings, adapters, electrical |
| Bronze CuSn8 | 8.80 | 8.80 | 16 – 26 | Bushings, wear parts |
| Copper Cu-ETP | 8.96 | 8.96 | 15 – 24 | Electrical, heat transfer |
| Zinc ZAMAK 5 | 6.60 | 6.60 | 6 – 11 | Die-cast style components |
| POM / Delrin | 1.41 | 1.41 | 9 – 16 | Bushings, gears, low friction |
| Nylon PA6 | 1.14 | 1.14 | 8 – 14 | Wear pads, rollers, guides |
| PTFE | 2.17 | 2.17 | 25 – 45 | Seals, chemical, low friction |
| PMMA (acrylic) | 1.18 | 1.18 | 9 – 16 | Windows, light guides |
| ABS | 1.05 | 1.05 | 7 – 13 | Housings, prototypes |
| PC (polycarbonate) | 1.20 | 1.20 | 10 – 18 | Impact-resistant covers |
| PEEK | 1.30 | 1.30 | 140 – 260 | High temperature, chemical, medical |
The formulas, in case you would rather work it yourself: a rectangular block is L × W × H, a round bar is π/4 × D² × L, a tube is the same with π/4 × d² × L subtracted, and a hex bar across flats A is 0.866 × A² × L. Work in millimetres, divide by 1000 for cubic centimetres, and multiply by the density above for grams.
Air freight charges on whichever is greater: actual weight, or volumetric weight, which is length × width × height in centimetres, divided by 6000. Small dense parts almost always ship on actual weight. Large light ones — a machined nylon housing, a plastic cover — ship on volume, and the invoice arrives at several times what the scale said.
The calculator shows both for your quantity. Freight is measured on the outside of the carton, not on the part, so it applies a 2.6× carton allowance over the part's own bounding volume to cover foam, voids and the box — which is about right for small machined parts packed properly. Solid metal parts will still bill on actual weight almost every time; it is thin-walled plastic and large hollow housings that flip over to volume.
If yours is going to bill on volume, that is worth knowing at design stage rather than at despatch. It is also one of the few times where a heavier material can be cheaper to ship, because the price stops moving once actual weight overtakes volumetric.
| What you actually have | What a quoting portal wants | How EKINSUN handles it |
|---|---|---|
| 3D CAD with mass properties | Accepted — the intended input | Accepted; we quote from it directly |
| A sketch with a few dimensions | Not accepted | Accepted; we work out volume, blank and weight ourselves |
| A photo with a caliper in the frame | Not accepted | Accepted; we scale from the caliper and confirm the critical dimensions with you |
| The old part, and no drawing at all | Not accepted | Accepted; measured or scanned, and you get the drawing afterwards |
| You do not know the material | Required field | We identify it from the part — density is one of the tests we use |
| You need one piece | Priced with a setup fee on top | MOQ 1, no separate programming fee |
Weight is genuinely useful to you — for shipping, for design decisions, for arguing with a supplier about material cost. It is not something you have to supply before we can price a part. See ordering with no CAD file, or work out what the machining itself should cost with the CNC machining cost calculator.
Weight equals volume multiplied by density. Work the volume out in cubic centimetres and multiply by the density in grams per cubic centimetre to get grams: a solid block is length times width times height, a round bar is pi divided by four times diameter squared times length, and a tube is the same with the bore subtracted. The part people usually get wrong is that a machined part has two weights that matter — the finished part, and the larger blank it was cut from, which is what you actually pay for.
2.70 grams per cubic centimetre, or 2700 kilograms per cubic metre. For quick mental arithmetic, a cubic centimetre of 6061 weighs 2.7 grams, steel weighs 7.85 grams and titanium Ti-6Al-4V weighs 4.43 grams. That makes 6061 roughly a third the weight of steel for the same shape, which is the single most common reason a part gets switched to aluminium.
The ratio of the raw blank weight to the finished part weight — in other words, how many kilograms you buy for every kilogram that leaves as a part. A ratio of 3 to 1 means two thirds of the metal you paid for became swarf. It matters commercially because you pay for the blank, not the part, and because on expensive materials such as titanium or PEEK the difference between a 2 to 1 and a 6 to 1 ratio can be most of the part cost.
Because stock has to be bigger than the finished part in every direction. A machining allowance of about 3 mm per side lets the cutter clean up the sawn faces, the scale or oxide layer, and any bow in the bar, and gives something to clamp. On a small part that allowance can easily double the purchased weight, which is why a 40 gram part can start life as a 90 gram blank.
Air freight is charged on whichever is greater, actual weight or volumetric weight, and volumetric is length times width times height in centimetres divided by 6000. Small dense parts almost always ship on actual weight, while large light parts such as machined plastic housings ship on volume and cost far more than their scale weight suggests. The calculator on this page shows both so you can see which one your shipment will be billed on.
Aluminium 6061 is about 34 percent of the weight of steel for the same geometry, but it is also roughly a third the stiffness, so a like-for-like swap that keeps every dimension identical will flex three times as much. The usual answer is to switch material and add section where it matters, which still lands well below the steel weight. The comparison table on this page shows the same part in every other grade so you can see the trade before committing.
No. Send the drawing, a sketch with dimensions, or a photo with a caliper in the frame and we work the weight out ourselves — along with the blank size, the material and the machining time. The weight is useful to you for shipping and for design decisions, but it is not something you have to supply before we can price a part.
Yes, free, instant, and with no sign-up or file upload. Every density it uses is printed on the page so you can check the arithmetic against your own reference, and the material prices are indicative small-quantity stock bands rather than tonnage figures.
Send a sketch, a photo with a caliper, or the part itself. We work out the weight, the blank and the price. No CAD needed, MOQ 1, reply in 12 h.
Send a drawing, a sketch, or a photo with a caliper next to the part — no CAD file needed. MOQ 1, quote back within 12 hours.
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