The Brew Caffeine Calculator
How much caffeine is actually in your cup? Pick your brew method and serving size to get an estimate — then see how it stacks up against daily limits.
How to use this calculator
Choose the method you brewed with, enter your serving size in fluid ounces (a standard mug is about 8 oz; a double espresso is about 2 oz), and set how many servings you've had. If you add your body weight, the calculator personalizes your daily limit — a 50 kg person and a 90 kg person don't process caffeine identically. The result shows your estimated milligrams, what share of a safe day that represents, and roughly how much more you can have.
These are estimates, not lab measurements. Real caffeine varies with the bean, the roast, and how you brewed. But they're built on published averages (USDA FoodData Central and FDA analyses), so they're accurate enough for everyday decisions.
The math, explained
Each brew method has a well-documented average caffeine content per fluid ounce. Drip coffee lands around 12 mg per ounce, so an 8 oz mug is roughly 95 mg. Espresso is far more concentrated at about 63 mg per ounce — but a double shot is only 2 ounces, so it totals around 126 mg, less than many people assume. Cold brew is the heavyweight: about 16 mg per ounce, because it's brewed at two to three times the coffee-to-water ratio of drip and steeps for 12+ hours.
Your daily limit comes from the FDA's widely cited 400 mg figure for healthy adults, adjusted down by body weight (about 5.7 mg per kilogram, per European Food Safety Authority guidance). If you're pregnant, the common medical guidance is to stay under 200 mg per day — and if you take medication or have a heart condition, ask your doctor rather than trusting a calculator.
Caffeine by brew method
| Method | Typical serving | Caffeine |
|---|---|---|
| Drip / filter | 8 oz | 70–140 mg |
| Pour-over | 8 oz | 90–150 mg |
| French press | 8 oz | 80–135 mg |
| AeroPress | 6 oz | 50–130 mg |
| Espresso (single) | 1 oz | 47–75 mg |
| Moka pot | 3 oz | 60–130 mg |
| Cold brew | 12 oz | 150–250 mg |
| Instant | 8 oz | 30–90 mg |
| Decaf | 8 oz | 2–15 mg |
Tips for managing your caffeine
Respect the half-life. Caffeine's half-life is about 5–6 hours, which means the 95 mg in your 3 pm coffee is still ~47 mg at 8 pm and ~24 mg at 1 am. If caffeine messes with your sleep, stop 8–10 hours before bed — and remember that "I don't feel wired" isn't the same as "it's out of my system."
Bean species matters most. Robusta beans contain roughly twice the caffeine of arabica (about 2.2–2.7% vs 1.1–1.7% by weight). A "strong" robusta blend can double your intake without changing your brew at all. Roast level has a much smaller effect than most people think.