A 9-inch chef knife drawn out, a full bar of 1084 on the rack — how much do you cut?
Blade length × width × thickness — counted at half thickness for the distal taper — plus the tang at full, divided by your bar's cross-section, with a grind-and-scale allowance you set: out comes the inches to cut, what it weighs, and what the steel costs. Everything stays in your browser.
The blade
The bar
The numbers here are yours to check. This page does arithmetic on what you type — it cannot see your recipe, your equipment or your batch.
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In MadeKeeper the same cut comes out of a bar you actually own — stock consumed by real inches at real cost, so every blade carries its true steel line from the rack to the ledger. See for bladesmiths or poke around the live demo. $19/mo for the whole back office, kept for as long as you stay. The shop stays free for cost a piece and one fair — no product cap. The tax packet, Etsy and Square, and more fairs are the $19.
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Every knife starts as a length of bar, and every forge forum has its own arithmetic for how long. The math below is the math this calculator runs — and where a number is a convention rather than a fact, it says so.
How much steel do I need for a 9-inch chef knife?
Take a 9 × 1.5 × 0.1875-inch blade counted at half thickness for the taper, add a 5 × 0.5-inch tang at the bar's full thickness, and you're holding about 1.73 cubic inches of steel. From 1.5 × 0.1875-inch bar that works out to 6.2 inches — call it 6.8 once the 10% grinding-and-scale allowance goes on. Weight is volume × 16.387 × 7.85 g/cm³ — carbon steel's density is physics, not a convention — which puts this knife at about 223 grams, just under half a pound, priced at whatever your bar stock runs per pound.
Why does it count the blade at half thickness?
That's the old estimating convention for a distal-tapered blade: it thins steadily from ricasso to tip, so the folk math averages it to half its stock thickness. But it is a convention, not a measurement, which is why it lives here as a setting instead of a buried assumption. A no-taper stock-removal blade keeps its full thickness the whole way, so you'd set the factor to 1.0 and count the entire bar.
How much extra do I add for grinding and scale?
Smiths argue this one anywhere from 10 to 20 percent, and both ends have a case — forge close to final shape and you lose less; hog it off the grinder under heavy scale and you lose more. The default here is 10%, which is what turns the example's 6.2 inches into 6.8, and it's yours to move. "Cut it long" is the ritual; the setting just tells you how long.
Can it tell me heat-treat or forging temperatures for my steel?
No — this page stops at stock arithmetic: how much bar to cut, what it weighs, what it costs. Heat treat and forge practice stay with your own process and your steel supplier's data for the exact alloy in your hand.