Roast loss calculator

Short answer. Roast loss % = (green in − roasted out) ÷ green in × 100. Twelve kilos of green dropping 10.2 kg roasted is 15%. Going the other way, green needed = roasted ÷ (1 − loss), so 100 kg roasted at 15% needs 117.6 kg of green — divide by 0.85, never add 15%. The same divisor prices the coffee: green at €8.00 a kilo costs €9.41 in every roasted kilo, and one percentage point of loss is worth about 11 cents a roasted kilo, or €1,345 a year at 12,000 kg.

The calculator

Enter one real batch — the green you weighed into the hopper and the roasted coffee you weighed out of the cooling tray — and the calculator works out your loss and every direction that follows from it: the green to buy for the roasted kilos you need, what a kilo of green yields, and what the green costs per roasted kilo. If you already know your loss figure, enter 100 green and your yield: 85 for 15%, 88 for 12%.

Roasters call the same number roast loss, shrinkage or weight loss; Röstverlust in German, quebra de torra in Portuguese, merma in Spanish. The arithmetic is the same in every language.

The roast loss formula

There is one number and three ways round it. Work in decimals — 15% is 0.15 — and keep every figure on the roasted weight, because that is what you sell.

• Roast loss = (green in − roasted out) ÷ green in × 100
• Roasted out = green in × (1 − loss)
• Green needed = roasted needed ÷ (1 − loss)
• Green in a roasted kilo = 1 ÷ (1 − loss)
• Green cost per roasted kilo = green price ÷ (1 − loss)

Worked example. You charge 12.00 kg of green and drop 10.20 kg. The loss is (12.00 − 10.20) ÷ 12.00 = 0.15, or 15%. To fill an order for 100 kg roasted you need 100 ÷ 0.85 = 117.6 kg of green. Each roasted kilo carries 1 ÷ 0.85 = 1.176 kg of green, and at €8.00 a kilo landed that is €9.41 of green in every kilo you bag.

The mistake worth naming: divide by one minus the loss, do not add the loss. Adding 15% to 100 kg gives 115 kg, which is 2.6 kg short of the 117.6 kg you actually need. A roastery doing 300 kg roasted a week is 7.9 kg of green short every week on that arithmetic, about 410 kg a year, or nearly seven 60 kg bags. It shows up as running out on a Thursday.

Roast loss by roast degree

These are the figures roasters quote each other, not a standard and not a specification. Treat them as a sanity check on a number you have measured, never as a substitute for measuring. If your own figure sits outside these bands there is nothing wrong with it; it means your green, your machine or your profiles are different, which they are.

Green columns are 1 ÷ (1 − loss) at each end of the band, rounded.

Overall, 12 to 18% covers most specialty roasting. Wikipedia's article on coffee roasting puts the range at 15 to 18% and attributes it "mainly to the loss of water but also of that of volatile compounds", which is the right shape of the answer.

The split matters more than the total. Green coffee arrives at roughly 10 to 12% moisture, and almost all of that water has gone by the time the batch is through first crack. So a 15% loss is broadly 10 to 12 points of water and 3 to 5 points of organic matter — sugars, cell structure and volatile compounds leaving as gas — plus about a point of chaff blown off to the cyclone. That is why a light roast cannot lose much less than about 12%: below that you have barely finished drying the bean. And it is why the extra loss of a dark roast is not water at all, but coffee.

How to measure your own roast loss

Roast loss is cheap to measure and expensive to assume. Cropster's September 2026 piece on the hidden costs in a growing roastery put the failure plainly: "yield assumptions stay at the number someone set when the machine was new." Green changes crop to crop. Profiles drift. The figure in the spreadsheet does not.

• One scale, both ends. Weigh green in and roasted out on the same scale. Two scales that disagree by 50 g on a 12 kg batch move your loss by 0.4 of a point, which is enough to matter in a price.
• Weigh what goes in the hopper, not what you scooped out of the sack. Beans left in the tub are not roast loss.
• Weigh out of the cooling tray, cooled. Coffee weighed hot off the drop is still losing water and reads light. Give it the same cooling time every batch so the number is comparable.
• Sweep the tray. The beans left in the corners are yours, and leaving them there inflates your loss.
• Record it per batch, next to the coffee, the batch size and the profile, on the run sheet. One batch is an anecdote. Four weeks of batches is your roast loss, and it will be different per coffee.

A roaster on r/roasting asked the question this way: "How do you get that shrinkage into your actual books so COGS and margins aren't fiction?" The answer is the run sheet. If the drop weight is written down every time, the average falls out of it, and the price list can be built on something real.

What changes roast loss

Moisture in the green

The single biggest input you do not control. A new-crop lot at 12% moisture loses more weight than the same coffee at 10% after six months in a dry warehouse. Green that dried out in your own store has already given you part of the loss, and you paid for that water on the invoice.

Density and processing method

A dense high-grown washed coffee and a softer natural taken to the same colour do not give the same number. Naturals and honeys carry more fruit residue into the roast and behave differently again.

Roast degree and development

The biggest lever you do control. Every extra minute after first crack takes dry matter with it. A profile change made for flavour changes your cost per kilo whether or not anyone repriced the coffee.

Drum temperature and airflow

More airflow carries away more moisture and more chaff. Two roasters running the same curve with different damper settings will not land on the same drop weight.

Batch size against drum capacity

The same profile at 8 kg and at 12 kg in a 15 kg drum gives different losses, because the ratio of coffee to heat and airflow changes. Record batch sizes separately rather than averaging across them.

Chaff and quakers removed

Chaff is part of the roast loss and goes to the cyclone. Quakers picked off the cooling tray or the sorting table are not roast loss, but they never reach a café either. Count them somewhere, or your yield per sack will not reconcile.

Why pricing off green weight loses money

A price list is written per roasted kilo, because that is the unit a café buys. A green invoice is per green kilo. If you take the green price straight into the cost of a bag, you have costed 1 kg of green into a bag that needed 1.176 kg, and you have understated the green in every kilo you sell by 17.6%.

That gap grows faster than the loss does. At 12% loss the green costs 13.6% more per roasted kilo than the invoice says; at 15% it is 17.6%; at 18% it is 22.0%. It is the most common reason a roastery's gross margin on paper is several points better than the one in its bank account.

Roast loss is the first line of a wholesale price, not an afterthought at the end. The wholesale coffee price calculator chains it through packaging, labour, delivery and overhead to a price per kilo at the margin you choose, and the wholesale price list template turns that into a sheet you can send a café. When green moves and you have to raise your prices, it is the divisor that decides how much.

What a wrong loss figure costs you

Worked example. Your price list assumes 14% loss. Your machine, measured over a month, is actually doing 16%. Green is €8.00 a kilo landed, and packaging and labour add €2.50 to a 1 kg bag. You price at a 40% gross margin.

The price was set once, off the wrong divisor, so it does not move. Two points of loss cost €0.22 on every roasted kilo, which is about €2,660 a year at 12,000 kg roasted, and it takes the margin from the 40% the list was built on to 38.9%. Nothing in the roastery looks wrong. The coffee sells, the invoices go out, and the money is simply not there at the end of the year.

One point at a time, here is what a point of loss is worth per roasted kilo, going from 15% to 16%, at a range of green prices. The cost of a point rises a little as the loss itself rises, so read these as the size of the thing, not a constant.

Roast loss and the green order

Roast loss is the conversion between the two halves of a roastery's week. Cafés order roasted kilos. Importers sell green kilos. Everything in between — the roast plan, the batches, the bags on contract — is one divided by the other.

Work backwards, always. Take the roasted kilos your confirmed and standing orders come to, add a buffer for samples, retail and the café that orders late, then divide by one minus your loss. Two hundred and twenty roasted kilos a week with a 10% buffer at 15% loss is 285 kg of green a week, and a thirteen-week contract is about 3,700 kg, or 62 bags of 60 kg. The roast plan calculator does that sum and turns it into batches, roast days and hours at the machine.

Use a different loss per coffee if your profiles differ. A filter lot dropped light and a dark espresso blend can be four points apart, which on a year's green is a different number of sacks, not a rounding error.

Questions roasters ask

What is roast loss in coffee?

Roast loss is the weight a batch loses between the green going into the roaster and the roasted coffee coming out of the cooling tray, written as a percentage of the green weight. Twelve kilos of green that drop 10.2 kg roasted lost 1.8 kg, which is 15%. Most of it is water leaving the bean; the rest is dry matter burnt off as gas and volatile compounds, plus the chaff blown to the cyclone. Roasters also call it shrinkage or weight loss.

What is a normal roast loss percentage?

Twelve to eighteen percent covers most specialty roasting, with lighter filter roasts at the bottom and darker espresso at the top, and dark roasts taken into second crack going past it. There is no standard and no right answer. The only figure worth pricing off is the one you measure on your own machine, with your own green, over a few weeks of real batches.

How much green coffee do I need for 100 kg of roasted?

Divide, do not add. Green needed = roasted ÷ (1 − loss), so 100 kg roasted at 15% loss needs 100 ÷ 0.85 = 117.6 kg of green, not 115 kg. At 12% loss it is 113.6 kg and at 18% it is 122.0 kg. Adding the loss percentage instead of dividing by it leaves you about 2.6 kg short on every 100 kg at 15%.

Why do dark roasts lose more weight than light roasts?

Because the loss keeps going after the water has gone. Green coffee arrives at roughly 10 to 12% moisture, and by first crack most of that has left. Every minute after that takes dry matter with it as the sugars and cell structure break down, so the longer and darker the roast, the more of the bean leaves as gas.

Does roast loss change with batch size?

Yes. The same profile on the same machine gives a different loss at 8 kg than at 12 kg, because the amount of coffee in the drum changes how heat moves into it and how much airflow each bean sees. If you roast the same coffee in two batch sizes, measure and record them separately rather than averaging them.

Is roast loss the same as shrinkage?

Yes, they are the same number under different names: roast loss, shrinkage, weight loss, Röstverlust in German, quebra de torra in Portuguese, merma in Spanish. Some roasteries use shrinkage more loosely to mean everything that never reaches a customer, including quakers picked out, samples and stale bags. Keep those separate, because you fix them in different ways.

Where Order Book fits

Order Book does not weigh your batches; your scale does, and this page does the arithmetic. What it does is hold the number where it is worth money. Each coffee in your catalog can carry its own green price and its own roast loss, so insights show the gross margin you are actually making per coffee and per client, at the real divisor rather than the one someone typed in two crops ago. When a lot changes, the margin moves where you can see it.

The other half is the roast plan. Confirmed orders close at the cutoff and become the plan for that round, grouped by coffee and stated in roasted kilos — which is the number this calculator turns into green.

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