Bar Stock Calculator — Parts Per Bar & Material Yield
How many parts actually come off a bar, once the parting-off kerf, the facing allowance and the bit the chuck cannot release are taken away. Then how many bars the batch needs, what percentage of the material becomes swarf, and what the metal really costs you per part — which is usually more than the part weight suggests.
Leave price blank for a yield-only answer. Densities come from our materials database.
Where the metal actually goes
Material yield is one of the quietest costs in a turned part. The weight of the finished component is easy to work out and easy to quote from — but it is not what you buy. You buy whole bars, and every part costs you its own length plus the parting-off kerf plus a facing allowance, while every bar ends in a stub too short to hold safely that goes in the offcut bin regardless.
On a short part in an expensive alloy those losses dominate. A 20 mm component parted with a 3 mm blade and faced by 1 mm consumes 24 mm of bar for 20 mm of part — before the remnant. That is a sixth of the material gone to swarf on geometry alone, and if the material is titanium or a nickel superalloy, that fraction is a real number on the quotation rather than a rounding error. This calculator shows the finished-part weight and the consumed-bar weight side by side, because the gap between them is the part of the material cost people forget to include.
The remnant deserves particular attention. A chucked bar needs enough length left to grip safely, and a bar-fed machine needs considerably more — the feeder cannot push the last section through, and that minimum is set by the machine rather than by the job. It is a fixed loss per bar, which means it is proportionally worst on short bars and on long parts where you only get a few pieces out of each length.
The useful move this enables is checking whether the part length and the bar length are working together. Because parts come in whole numbers, there are step changes in yield: a small reduction in a facing allowance, or buying 3.5 metre bars instead of 3 metre, can occasionally add a whole extra part per bar and drop the material cost per piece by several per cent for no change to the component at all. The tool flags when you are close to one of those steps, since it is worth knowing before the order goes in.
None of this replaces a proper quotation — material is only one line of it, and on a complex part the machining time usually dominates. But it is the line that scales directly with batch size, so on a long production run it is worth getting right. If you want the full picture on a specific component, send the drawing and you will get a costed quote back with a free DFM review that names what is actually driving the price.
Bar stock and material yield — FAQ
How do I calculate how many parts I get from a bar?
Take the usable bar length (total length minus the remnant your chuck or bar feeder cannot use), then divide by the length each part consumes — the finished length plus the parting-off blade width plus any facing allowance. Round down to a whole number, because a partial part is no part at all.
What is a typical parting-off blade width?
Commonly 2 to 4 mm for general turning, with 3 mm a frequent default. Narrower blades waste less material but are more prone to deflection and breakage, particularly at larger diameters where the blade has to reach further to the centre. On expensive materials the saving from a narrower blade can justify the extra care.
Why does the remnant matter so much?
Because it is a fixed loss on every bar regardless of what you make. A chucked bar needs enough length to grip safely; a bar feeder typically needs much more, because it cannot push the final section through. On short bars or long parts that fixed loss becomes a large share of the material, and it is entirely independent of how efficient the rest of your cutting plan is.
How is the material cost per part worked out?
From the volume of bar each part consumes — not the volume of the finished part. Consumed length times the bar cross-section gives a volume, multiplied by the material density gives a mass, multiplied by the price per kilogram gives the cost. The difference between that figure and the finished-part weight is the material you paid for and turned into swarf.
Does a longer bar always give better yield?
Usually but not always, and the gain is not linear. A longer bar spreads the fixed remnant loss across more parts, which helps. But because parts come in whole numbers there are step changes: sometimes a longer bar adds no extra part at all and simply leaves a bigger offcut. It is worth checking the actual numbers for your specific part length rather than assuming.
Can you machine from customer-supplied material?
Yes — free-issue material is common and we handle it routinely. The main things worth agreeing up front are how much material to allow for setup and first-off, and what happens if a bar is out of specification or damaged, since with free issue there is no stock to fall back on. Full traceability is maintained either way.
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