How Much Caffeine Is in Coffee? (Calculator)

Dose is the primary lever. Doubling the coffee you use doubles the caffeine available before extraction even begins. Brew method determines the extraction fraction, but the range across hot methods (filter, espresso, French press) is narrower than most people expect—typically 85 to 95%. Cold brew extracts somewhat less by temperature, but long steep times and high dose weights close the gap.

Species matters more than roast. Robusta averages roughly 2.7% caffeine by dry mass; Arabica averages around 1.4%. A Robusta-heavy espresso blend produces nearly twice the caffeine of a single-origin Arabica at the same dose. If your commercial espresso blend feels strong, caffeine content is a likely contributor.

Caffeine in coffee is one of those numbers people want to be precise about and cannot be. The variance in raw caffeine content across Arabica origins alone is wide enough that a 30 g dose of Yirgacheffe and a 30 g dose of Guatemalan Bourbon from the same roast profile might differ by 30 to 40 mg before you factor in grind and extraction. The formula here gives a working estimate, not a measurement.

The practical numbers: a standard 15 g filter dose of Arabica produces somewhere in the 120 to 180 mg range. A double espresso (18 g) runs 90 to 120 mg, lower than most people expect, because the shot volume is small even at high concentration. Cold brew concentrate is the wildcard; a long steep at 1:8 with 100 g of coffee produces a concentrate with substantial caffeine per ounce, but the serving size usually stays small (60 to 90 mL).

Dark roast has slightly less caffeine than light roast by mass. Roasting degrades caffeine, but only modestly at commercial roast levels (roughly 5% from light to dark). The folk wisdom that dark roast is “stronger” refers to flavour intensity, not caffeine content. A light roast by the same dose weight will generally have more caffeine.

The FDA’s 400 mg per day reference for healthy adults is the standard public health guidance in the US. It is not a hard limit; it is a “generally recognized as safe” figure for most adults. Pregnant individuals, people on certain medications, and those with heart conditions have different thresholds. The calculator displays the FDA figure as context, not as a personal recommendation.

If you are tracking caffeine for health reasons, a refractometer-based measurement of your specific brew is more accurate than this or any other formula. Use this calculator for a working estimate and planning, not precision management.