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A kilo of salmon on the invoice is never a kilo of salmon on the plate. Between the two sits skin, bone, fat and the weight heat takes off again — and anyone costing a dish on the purchase weight is costing it on a kilo that doesn't exist.
Every kitchen buys a whole salmon side, a beef tenderloin, a crate of onions — and prices the dish off that purchase price per kilo. That's the arithmetic error this whole article explains: the kilo that comes off the delivery van is never the kilo that lands on the plate. Skin, bone, silverskin, fat, peel, stem and root come off before anything even hits the pan, and then the product loses weight again to heat.
The gap between those two weights is called the yield percentage — in the trade literature, AP (as purchased, the weight you bought) versus EP (edible portion, the usable weight). Every cook learns this as the "butcher's test" in culinary school, and yet almost nobody actually applies it: most kitchens still price a dish off the purchase price per kilo, full stop. The result is a cost price that looks sharp and isn't.
This isn't a new or niche idea — it's standard knowledge in every professional culinary program, and whole reference works exist just to publish yield-percentage tables per product. But search this site, the trade press, or an average costing conversation for "yield percentage", and you'll find nothing. The site's own recipe costing tool has carried a yield field on every ingredient since day one, and nine visitors in ten simply leave it at 100%.
This guide walks the seven numbers one by one: the formula, what fish, meat and produce typically lose, why cooking loss stacks on top of trim loss, and what all of that does to your real food cost. Below, plug your own purchase price, your yield and your menu price into the calculator and see in euros per year what you're currently not seeing.
Why your cost price looks healthier than it is
The mistake is almost always the same one: dividing the purchase price per kilo by the number of kilos on the invoice, and using that figure as though it were the cost of the usable product. For a bag of rice or a bottle of oil that's fine — almost nothing is lost between the bag and the pan. For a whole fish, a bone-in cut of meat or a fresh vegetable it isn't, and the gap is rarely small.
The yield percentage is simply defined: the usable weight after trimming and cooking, divided by the weight you bought. At 60% yield you're paying for 1,000 grams to get 600 grams onto the plate — you did pay for the other 400 grams, they just never show up on the guest's bill. Cost a dish on the purchase weight instead of the usable weight and you understate the cost price by exactly that gap.
And that gap builds in two places. First, trim loss: skin, bone, silverskin, fat, peel, stem, root — everything that comes off before the product ever reaches the pan. Then cook loss: the moisture and fat that meat and fish lose again to heat, whether that's searing, roasting or braising. Both are normal and unavoidable. The problem isn't that they exist — the problem is that most cost calculations act as if they don't.
The ultimate guide Menu Engineering & Drinks: 6 Steps to More Margin From menu design to pour cost: everything your menu can earn you, in one guide. Open the guideThe 7 numbers, and what each one costs you
They're ordered from most universal to most specific. The first is the formula that applies to every ingredient. Then fish, meat and produce, one at a time — because each category loses differently — and only after that the number most kitchens skip entirely.
1. The formula that changes everything: cost price is purchase price divided by yield
The arithmetic already sits inside the site's own recipe costing tool, in the very example every new user opens on: minced beef at €9.80 per kilo, at 95% yield. Most of the ingredients in that same seed list — tinned tomatoes, spaghetti, parmesan, olive oil — sit at 100%: what you buy is what you use. Minced beef doesn't: it sheds moisture and fat while it browns, and that translates to a 95% yield.
The formula is one line: true cost price = purchase price ÷ (yield ÷ 100). For the minced beef that's €9.80 ÷ 0.95 = €10.32 per kilo — a 52-cent gap that's almost negligible at 95% yield. At 60% yield, entirely normal for a whole fish or a bone-in cut, the same arithmetic bites hard: €9.80 ÷ 0.60 = €16.33 per kilo. Sixty-six percent above what the invoice says.
That's exactly what the yield field in the recipe costing tool does — and exactly why the field sits on every ingredient individually rather than once for the whole recipe: minced beef, tomatoes and spaghetti each lose their own share, and a dish combining all three has a cost price that depends on all of those percentages together. Leave the field at 100% for an ingredient that yields less, and the tool faithfully adds up what you typed — and what you typed was wrong.
2. Fish: a whole salmon side commonly yields 65 to 70% usable fillet
A whole salmon side with skin and pin bones costs a set amount per kilo on the invoice. After skinning it, pulling the pin bones with tweezers and trimming the thin belly flap, what's left in practice is typically 65 to 70% as usable fillet — the rest is skin, bone and trim you can, at best, still turn into stock.
Run that through the formula above and the real cost per usable kilo lands roughly 45% above the invoice price. A salmon side at €25 per kilo becomes something like €36 to €38 per usable kilo — before a single pan has even been heated. Anyone basing their menu price for a salmon dish on the invoice price alone is working from a figure that's nearly half too low.
Round fish with bone in (whole sea bass or bream, say) usually lands a little lower again than a flat filleting fish, precisely because there's proportionally more bone and head. A pre-filleted, boned purchase costs more per kilo on the invoice, but the yield is already priced in — the comparison that matters is always the price per usable kilo, never the invoice price per kilo on its own.
3. Meat: a beef tenderloin trimmed to chateaubriand standard often gives back only 55 to 65%
Of everything a kitchen buys, the beef tenderloin is the clearest example, and the number most often costed wrong. A whole tenderloin carries the chain (the thin strip of muscle along one side), the silverskin, and a layer of fat, all of which come off before you're left with a chateaubriand-worthy piece. What remains after that trimming is typically 55 to 65% of the weight you bought.
On a tenderloin at €42 per kilo, 60% yield means a real cost of €70 per usable kilo — nearly seventy percent above the invoice price. That's the widest gap of any example in this article, and it's exactly why a chateaubriand costs so much on the menu: not because the supplier charges an inflated price, but because almost two kilos sat on the cutting board for every usable kilo that made it to a plate.
The trim isn't wasted if you count it: the chain and silverskin go into mince, tartare or stock, and that recovered value should, in principle, be subtracted from the headline cut's cost. Most kitchens don't do that, which makes the yield figure above even more conservative than it already looks — it's a floor, not an exact number.
4. Produce: yield swings enormously by vegetable, and 10% is not a universal rule
Produce is where a single rule of thumb gets applied to everything — "assume 10% waste" — and that habit is itself a costing error, because the gap between vegetables is large. An onion typically loses only 10 to 15% to peel and root, a yield of roughly 85 to 90%. A bell pepper loses more to stem, seed core and the white pith inside: typically 20 to 25%, a yield of around 75 to 80%.
Fresh herbs and leafy greens sit at the other end of the scale. Parsley, basil, spinach: after removing thick stems and wilted leaves, sometimes only 60 to 70% remains, and that's before anything is even blanched or cooked. A kitchen that costs its entire produce line at the same flat percentage understates the expensive lines and overstates the cheap ones.
The point isn't that every product needs its own precise figure — it's that one rule of thumb for the whole store room creates a false sense of certainty. An onion at 87% and parsley at 65% are not a rounding difference from each other; they're two different products with a cost gap of more than twenty percentage points of yield.
5. Cooking loss stacks on top of trim loss — and that's the step most kitchens skip
Trim loss happens before the product hits the pan. Cook loss happens after: meat and fish shed further moisture and fat to heat, and how much depends on the method. A quick sear typically costs 10 to 15% of the weight that was still there. Roasting or pan-frying runs to 20 to 25%. Slow braising or confit can push toward 30%, because the product gives off moisture for hours.
The mistake almost every kitchen makes is adding trim and cook loss together instead of multiplying them. At 69% trim yield and 85% cook yield, the combined yield is not 69 + 85 − 100 = 54%. It's 0.69 × 0.85 = 0.5865 — nearly 59%. That looks like a small difference on paper, but on a salmon side at €25 per kilo it's the difference between a cost of €42.37 (correct, multiplied) and €46.30 per usable kilo (wrong, added) — an error that can push the cost price the wrong way in either direction depending on how the addition is done.
Keep the rule as one sentence: yield compounds, it doesn't add. Every step — trimming, further trimming, cooking — acts on whatever was left after the previous step, never on the original purchase weight. That's exactly what the graphic below shows: three ingredients, and how much of the original kilo survives each step.
Three ingredients, the same purchase kilo. Trim loss comes off first, then — for fish and meat — cook loss on top. What's left at the bottom is what actually reaches the plate.
The beef tenderloin loses the most: less than half of every purchased kilo survives to the plate. The onion loses the least, and loses nothing further to cooking — its number stops at trimming. That's exactly why one rule of thumb for the whole store room never holds.
6. The blind spot, quantified: what invoice-based costing does to your real food cost
Cost a salmon dish off the invoice price instead of the true cost per usable kilo, and that dish's food cost looks artificially low — sometimes half of what it really is. For one dish on a thirty-item menu that might seem minor. For a menu where half the mains are fish or bone-in, skin-on meat, it adds up to a blended food cost that looks structurally healthier than it is.
For comparison: a healthy food cost for a bistro typically runs 28 to 34% of revenue excluding VAT, and 30 to 38% for a fine-dining operation — figures from this site's own restaurant benchmark. An operator costing their menu on invoice prices instead of true EP cost might see a food cost of 20% and think they're comfortably inside that band, when the real, compounded cost price actually sits them squarely in the middle of it — not bad, but not the exceptional number they thought they were steering by.
That's the whole blind spot: it isn't a disaster that closes the business, it's a number that makes you systematically too optimistic about exactly the dishes with the lowest yield — fish and bone-in, skin-on meat. And those are usually not the cheapest items on the menu; they're often the mains where the margin is needed most.
One salmon main course, 180 g on the plate. Left: the mistake most menus make — costing off the invoice price. Right: the true cost, after both trim and cook loss.
Costed off the invoice
True cost (EP)
A gap of almost thirteen percentage points isn't a rounding error — it's the difference between a dish that looks spectacularly profitable and a dish that's simply healthy. At ninety portions a week that gap is over fourteen thousand euros a year that never shows up anywhere in the books as "wrong", because no mistake was made — the number was simply never calculated.
7. The fix already exists: the yield field and the five-minute butcher's test
The site's own recipe costing tool has carried a yield field next to every ingredient since its first version. Fill in the real percentage there and the tool automatically calculates the correct cost per usable kilo — and that cost flows through to every recipe and sub-recipe that uses the ingredient. Leave the field at its 100% default and the tool faithfully computes with a number that, for most fresh product, simply isn't true.
Finding the real number doesn't require a reference book: measure it yourself, once per ingredient, with the classic butcher's test taught in every culinary program. Weigh the product as it arrives (that's the AP weight). Trim it the way you normally would — skin off, bone out, silverskin away. Weigh the usable result. Divide the second weight by the first and multiply by a hundred: that's your yield percentage. Five minutes of work, once per supplier and product, and the number rarely shifts enough to need repeating often.
Do that for your ten most important ingredients — the fish, the meat, the expensive produce — and the rest of the menu can stay safely at 100% wherever little to nothing is actually lost. This isn't about precision on every single item; it's about the ten lines where the gap runs into hundreds of euros a month.
Put your own ingredient next to your own menu price
Fill in what you buy, what's left after trimming and cooking, and what the dish costs on the menu. The fields start with the salmon example above so you can see how it reads — overwrite them with your own.
The calculator shows four numbers: the true cost per usable kilo, the food cost you'd see if you (wrongly) costed off the invoice price, the true food cost against your menu price, and the difference in euros per year based on how many portions you sell a week.
Yield scan
One ingredient, your own numbers, and the difference in euros per year.
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This is the exact same formula as the yield field in the recipe costing tool: cost price = purchase price ÷ (trim yield × cook yield). Everything runs in your browser; nothing is sent or stored.
Two things to remember when reading this. Trim and cook yield multiply, they don't add — that's the mistake most manual calculations make, and it's what this calculator gets right automatically. And the portion weight is the weight on the plate, after preparation: for fish and meat that's already after cook loss, which means you need slightly less raw product per portion than you might first assume.
The gap that's left isn't a sign something's wrong with your business — it's the number that was always there and was never counted. The higher your share of fish and bone-in, skin-on meat on the menu, the bigger that gap gets.
What to do with this this week, this month and this quarter
Reweighing every ingredient in the kitchen at once is beyond anyone. This order works, because each step makes the next one measurable.
This week — measure your three most expensive ingredients
- Pick the three ingredients that appear most on your menu and have the lowest yield — usually fish, bone-in meat and the pricier produce.
- Run the butcher's test once per ingredient: weigh in, trim as usual, weigh out. Note the percentage.
- Enter those three percentages into the yield field of the recipe costing tool and see what changes in the cost of the dishes that use them.
- Don't touch a single price this week — see first, decide later.
This month — extend it across the whole menu
- Measure the yield of every ingredient that appears on a plate more than once a week and shouldn't be left at 100%.
- Recost every main course with the true cost prices and set them next to your current menu prices.
- Find the two or three dishes with the biggest gap — usually the ones with fish or bone-in, skin-on meat.
- For those dishes, check whether the trim (chain, silverskin, bones) is usable elsewhere — a stock or a mince preparation recovers part of the gap.
This quarter — build it into how you work
- Add yield measurement to your onboarding process for new suppliers — a single season can shift a product's percentage.
- Only revisit menu prices for dishes where the true food cost sits above your own target band — not everything at once.
- Track it alongside your ingredient prices — a supplier who raises the price and lets the trim get worse costs you twice.
- Fold it into your quarterly review together with your benchmarks — yield is the number that finally makes food cost honest.
The kilo on the invoice isn't the kilo on the plate
Almost every kitchen that runs this calculation for the first time finds the same thing: the purchase prices are fine, the menu prices aren't unreasonable, and yet somewhere between the delivery van and the plate, fifteen to forty-five percent of the true cost went missing — not lost, just never counted.
That's good news, because fixing it costs nothing: no extra purchasing, no price rise, just a number that should have been counted all along. One butcher's test per ingredient, one field filled in on the recipe costing tool, and a dish's cost price finally matches what it actually costs to make.
Then do the same with the other half of your purchasing. Food cost as a whole and portion size run on exactly the same logic: what you don't measure, you can't steer — and yield is the number most kitchens have never measured.