Coffee science
How we estimate caffeine and CGA
Last reviewed 7 Nov 2026
Every caffeine and CGA figure on this site is an estimate, unless it says it was measured. This page explains where the numbers come from.
Each roast lot has its own figures
Each lot's figures come from its roast data: how much the beans weighed before and after roasting. Beans get lighter as they roast, mostly from losing water, and that change tells us how far the roast went.
Typical values for the bean type
We combine that with typical caffeine and CGA values for the bean type, Robusta or Arabica. The result is worked out per gram of roasted coffee.
A middle value, with a range
Each figure is a middle estimate, which is the number you see, with a range behind it in the ⓘ next to it. Grind, water temperature and brewing time change the real amount in your cup, so treat every figure as a guide.
CalculatorLab results replace estimates
When a lot is tested by a lab, the lab result replaces the estimate, one figure at a time. The site then says "measured", with the date of the result.
Research changes. These summaries reflect the studies available on the date shown, and we update them as new evidence appears. They are general information, not medical advice.