Caffeine Safety Calculator
Caffeine is the most widely consumed psychoactive substance in the world. The FDA states that 400 milligrams per day is generally considered safe for healthy adults, roughly equivalent to four 8-oz cups of brewed coffee. However, individual sensitivity varies, and pregnant women are advised to limit intake to 200 mg per day. This calculator adds up caffeine from up to five sources (coffee, tea, energy drinks, sodas, supplements, or other foods) and shows your total against the FDA 400 mg threshold, as well as how much headroom you have or how far you are over the limit. Enter the milligrams of caffeine in each source and the number of servings consumed.
For each source, enter mg per serving and number of servings.
Caffeine safety formula
Total caffeine (mg) = sum(mg per serving * servings)
% of limit = Total / 400 * 100
Headroom = 400 - Total (positive = under limit)
The FDA safe upper limit for healthy adults is 400 mg of caffeine per day. Pregnant women should limit to 200 mg per day per FDA guidance.
Common caffeine sources
- 8 oz brewed coffee: 80-100 mg (varies with roast and brew method).
- Single espresso shot (1 oz): 60-70 mg.
- 8 oz black tea: 40-70 mg; green tea 20-45 mg.
- 12 oz cola soft drink: 30-40 mg.
- 8 oz energy drink: 70-150 mg (check label; products vary widely).
- Pre-workout supplement (1 scoop): 150-300 mg (check label).
Caffeine safety calculator: frequently asked questions
How much caffeine is safe per day?
The FDA states that 400 mg of caffeine per day is not generally associated with dangerous negative effects for healthy adults. This is roughly equivalent to four 8-oz cups of brewed coffee. Pregnant individuals should limit intake to 200 mg per day or less.
How much caffeine is in common beverages?
Approximate caffeine content: 8-oz brewed coffee 80-100 mg, espresso shot 60-70 mg, 8-oz black tea 40-70 mg, 8-oz green tea 20-45 mg, 12-oz cola 30-40 mg, 8-oz energy drink 70-150 mg (varies by brand).
What are the signs of too much caffeine?
Symptoms of caffeine overconsumption include rapid or irregular heartbeat, insomnia, nervousness, restlessness, nausea, headache, and anxiety. Very high doses (generally above 1,200 mg in a short period) can cause serious health events and should be avoided.
Does caffeine sensitivity vary between people?
Yes. Genetic differences in caffeine metabolism (particularly CYP1A2 enzyme variants) mean some people metabolise caffeine two to four times faster than others. Body weight, medications, liver health, and habitual intake also affect tolerance. The 400 mg FDA guideline applies to healthy adults in general.
Is caffeine in food counted the same as in drinks?
Yes. Caffeine from all sources, including chocolate, coffee-flavored desserts, energy bars, and certain medications, contributes to your total daily intake. Dark chocolate (28 g) contains approximately 20 mg; milk chocolate has around 6 mg.
Official sources
- FDA: Spilling the Beans: How Much Caffeine is Too Much?
- USDA FoodData Central: FoodData Central (caffeine per food).
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.