How to use the coffee roast loss calculator
- Choose what to find: the roasted weight, the green weight to buy, or the percent lost.
- Pick the unit: grams, kilograms, ounces or pounds.
- Enter the two values the chosen mode needs. The loss percent in the form is an example, so measure your own.
- In More options, enter a green price per pound to see the cost of the batch and the cost per pound of roasted coffee.
Formula
roasted = green x (1 - loss / 100)
green = roasted / (1 - loss / 100)
loss = (green - roasted) / green x 100
The loss is measured against the green weight. For cost, the green price is per pound, so the cost of the batch is the green pounds times the price, and the cost per roasted pound is that cost divided by the roasted pounds.
1,000 grams of green coffee at 15% loss
1,000 g of green coffee that loses 15% weighs 1,000 x 0.85 = 850 g when roasted, which is 150 g lost. To end with 850 g you need 850 / 0.85 = 1,000 g of green. Going the other way, 1,000 g green and 850 g roasted is a (1,000 - 850) / 1,000 = 15% loss. You need 1.1765 g of green for each gram of roasted.
For 8 lb of roasted coffee at 14% loss, buy 8 / 0.86 = 9.302 lb of green. At $5.50 a pound green, 1,000 g costs $12.13, and each roasted pound costs 12.13 / 1.874 = $6.47.
Where the weight goes
Green coffee beans hold moisture, and roasting drives most of it off, along with a little chaff. That is why the roasted beans weigh less than the green beans you started with. The loss grows as the roast gets darker, because more moisture and some solids leave. Results differ by bean, by moisture and by roaster, so the percent in the form is only an example.
To find your own number, weigh a batch before and after roasting, and use the mode that finds the percent lost. Do this for a few batches of the same coffee and the same roast level, then use the average. Once you know it, the green weight to buy for a target roasted weight is a simple division.
Using the numbers
The loss matters for buying and for pricing. A coffee that costs $5.50 a pound green costs more per pound roasted, since you pay for the weight that disappears. The cost mode shows that effect, and the figure is only the cost of the green coffee. It does not include labor, packaging, fuel or waste.
For brewing amounts from roasted coffee, use the Coffee Ratio Calculator, and for the yield of an espresso shot the Espresso Yield Calculator. The Unit Price Calculator compares prices of different bags, and the Recipe Cost Calculator works out the cost of a recipe.
Assumptions and limits
- The loss is from 0 up to but not including 100 percent, with at most three decimals.
- Roasted coffee weighs less than green coffee, so the roasted weight cannot exceed the green weight.
- Cost uses only the green price per pound you enter. Labor, packaging and waste are not included.
- Nothing is stored or uploaded.
Frequently asked questions
How much weight does coffee lose when roasted?
It varies with the bean, its moisture and the roast level, and it grows as the roast gets darker. The 15% in the example is only a starting point. Weigh your own batches to find your number.
How much green coffee do I need for a pound of roasted?
Divide the roasted weight by one minus the loss. With a 15% loss, 1 lb of roasted needs 1 / 0.85 = 1.1765 lb of green coffee.
How do I calculate my roast loss percentage?
Subtract the roasted weight from the green weight, divide by the green weight and multiply by 100. For 1,000 g green and 850 g roasted, the loss is 15%.
Why does roasted coffee cost more per pound?
Because you pay for the green weight and keep less of it. At a 15% loss, a pound of roasted coffee carries the price of about 1.18 pounds of green coffee, before any other costs.