Coffee Roast Loss
Calculate weight loss during coffee roasting. Determine how much green coffee you need to achieve your target roasted weight at any roast level.
About this calculator
Coffee beans lose a substantial share of their weight during roasting, mostly as moisture and volatile gases driven off by heat, and the darker the roast, the more of that weight disappears. This calculator applies conventional roasting-industry loss percentages by Roast Level -- roughly 12% for Light, 15% for Medium, 18% for Dark, and 22% for Very Dark -- to a Green Coffee Weight to find the Roasted Weight and Weight Lost. Roast Level is the sole determinant of Loss Percentage: Green Coffee Weight has no effect on that percentage at all, since the loss is expressed as a share of the starting weight rather than a fixed gram amount.
Green Coffee Weight, on the other hand, drives both Roasted Weight and Weight Lost directly and proportionally -- doubling the amount of green coffee you roast doubles both the final roasted weight and the grams lost along the way, at any roast level. This relationship is useful in both directions: a home roaster can use it to figure out how much green coffee to buy for a target bag size, while a roastery can use it to plan batch sizes and yields when scheduling multiple roasts.
Inputs
Results
Roasted Weight
850 g
≈ 8 sticks of butter
How to Use This Calculator
- Enter the weight of green (unroasted) coffee in grams.
- Select the roast level: light (12%), medium (15%), dark (18%), or very dark (22%).
- The calculator shows roasted weight in grams, weight lost during roasting, and loss percentage.
- Use roasted weight to plan packaging quantities and pricing per 12 oz bag.
How the result changes with Green Coffee Weight (g)
| Green Coffee Weight (g) | Roasted Weight |
|---|---|
| 500 | 425 g |
| 750 | 637.5 g |
| 1,500 | 1,275 g |
| 2,500 | 2,125 g |
What each input means
- Green Coffee Weight (g)
- Weight of unroasted green coffee beans in grams before roasting.
- Roast Level
- Darker roasts lose more moisture and organic material during roasting.
How this is calculated
Worked example, using the default values
- Identify Input ParametersGreen Coffee Weight (g) = 1000, Roast Level = 2 = 2 input(s) provided
- Calculate Roasted WeightRoasted Weight850 = 850
- Calculate Weight LostWeight Lost150 = 150
- Calculate Loss PercentageLoss Percentage15 = 15%
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Does the amount of green coffee change the percentage lost during roasting?
No -- Green Coffee Weight is completely inert against Loss Percentage, which is set entirely by Roast Level. A 100g batch and a 10,000g batch roasted to the same level both lose the identical percentage of their starting weight, since that loss is expressed as a share of the green weight rather than a fixed gram figure.
How much more coffee do you lose roasting dark versus light?
Roast Level is the sole factor behind Loss Percentage -- Light roasts lose roughly 12% of green weight, while Very Dark roasts lose roughly 22%, nearly double. That's why a bag of dark-roast beans typically requires noticeably more green coffee to produce the same finished weight as a light roast.
If I roast twice as much green coffee, do I get twice as much roasted coffee?
Yes -- raising Green Coffee Weight always raises Roasted Weight in direct proportion at any roast level, since the loss is applied as a fixed percentage of the starting weight. Doubling your green coffee input doubles both your roasted output and the total grams lost to roasting.
How much green coffee do I need to end up with a 12 oz bag of roasted beans?
Work backward from the Roasted Weight you want using your chosen Roast Level's loss percentage -- for a Medium roast at roughly 15% loss, you'd need about 18% more green coffee than your target roasted weight, since Green Coffee Weight scales the Roasted Weight proportionally at any fixed roast level.
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