Coffee Roast Weight Loss Calculator｜Track Roast Yield and Stage
Enter your green and roasted weights to see the grams lost, the roast weight loss percentage, and a light, medium, or dark stage guide on one screen. A simple way to log home batches and repeat a roast you liked.
💡 About this tool
Once you start roasting at home, you want a number that tells you how far a batch developed. Color and smell drift with your lighting and your eye, so they are hard to repeat. Weight loss percentage fixes that: it measures how much of the green weight burned off as moisture and gas during the roast, and it climbs the deeper you go.
Drop in the green and roasted grams and this tool returns the weight lost and the loss percentage, plus a rough roast stage. A scale is the most repeatable instrument in your setup — anyone weighing the same batch gets the same number, unlike a color call under kitchen light. Log the figure for every roast and you build a paper trail you can actually reproduce.
🧐 Frequently Asked Questions
How is roast weight loss calculated? Loss % = (green weight − roasted weight) ÷ green weight × 100. For example, 250 g green and 210 g roasted gives (250 − 210) ÷ 250 × 100 = 16.0%.
What is a normal weight loss percentage? Home roasts usually land between 12% and 20%. Lighter roasts sit around 11-13%, darker roasts can pass 20%, and the green bean's starting moisture (typically 10-12%) shifts the result.
How do I read the roast stage? This tool treats under 13% as light, 13-17% as medium, and 17% and up as dark. These are reference bands and will shift with the bean and the roaster.
What does too low or too high a loss mean? Below the 11-13% range, beans are often underdeveloped, with grainy, cereal-like flavors. Push too high and you get roasty, bitter, overdeveloped notes.
Where does the lost weight go? Most of it is water. Green coffee carries moisture that evaporates in the drum; smaller amounts of carbon dioxide and roast byproducts are driven off too. The bean expands in volume but drops in weight.
📚 Weight loss as a development gauge
Roasters lean on weight loss because it is one of the few roast measurements that does not depend on a subjective eye. A higher percentage means the beans went further into development; a lower percentage means a lighter roast. That makes it a quick consistency check between batches: if last week's favorite landed at 15.2% and today reads 12.8%, you stopped earlier than you meant to.
It pairs well with, but does not replace, taste. Coffee that loses moisture below roughly 11-13% often reads grainy and underdeveloped in the cup, while very high loss skews roasty and bitter. Logging the percentage next to your tasting notes turns a fuzzy memory into a target you can dial back into next time.