mg per drink · daily guidance · bedtime estimate
Caffeine calculator
Add the day’s coffee, tea and other drinks to see your total against published guidance, and roughly how much may still be in you at bedtime. General guidance, not medical advice.
Your day
- Today175 mg44% of 400 mg
- Left at bedtimeabout 25 mgrough estimate; 5–64 mg with a 2–8 h half-life
- Bedtime23:00a 4 h half-life for the middle figure
| Time | Drink | Caffeine | Remove |
|---|---|---|---|
| 08:00 | Brewed coffee15 h before bed | 95 mg | |
| 13:00 | Black tea10 h before bed | 47 mg | |
| 16:00 | Cola7 h before bed | 33 mg |
How the totals and the bedtime estimate work
Each drink uses the caffeine USDA FoodData Central gives per 100 g, times the serving weight it lists: about 95 mg for an 8 fl oz cup of brewed coffee. Real cups vary with the beans, leaf and strength (the FDA gives 113–247 mg for 12 fl oz of brewed coffee), so add your own figure if you know it.
The total is compared with 400 mg, the amount the FDA cites for most healthy adults and the daily intake EFSA found raises no safety concerns for healthy adults other than pregnant women. Tick “Pregnant or breastfeeding” to compare with 200 mg: ACOG says intake under 200 mg a day does not appear to be a major factor in miscarriage or preterm birth, and EFSA found up to 200 mg a day raises no safety concerns in pregnancy or while breastfeeding. A serving over 200 mg is flagged, as EFSA’s single-dose level for adults is up to 200 mg. For children and teenagers EFSA uses 3 mg per kg of body weight a day.
Left at bedtime is a rough estimate. It treats each drink as absorbed at once and halving every few hours. EFSA puts caffeine’s half-life at about 4 hours on average in healthy adults, with a range of 2 to 8 hours depending on age, body weight, pregnancy, medication and liver health; the middle figure uses 4 hours and the range 2 and 8. EFSA notes that 100 mg close to bedtime may affect sleep in some adults.
Sources
| Drink | Serving | Caffeine | FDC entry and working |
|---|---|---|---|
| Brewed coffee | 8 fl oz cup (237 ml) | 95 mg | FDC 171890: 40 mg per 100 g × 237 g |
| Brewed coffee | 12 fl oz mug (355 ml) | 142 mg | FDC 171890: 40 mg per 100 g × 355.2 g (12 × FDC's 29.6 g per fl oz) |
| Espresso | single, 1 fl oz (30 ml) | 63 mg | FDC 171891: 212 mg per 100 g × 29.6 g |
| Espresso | double, 2 fl oz (60 ml) | 126 mg | FDC 171891: 212 mg per 100 g × 59.2 g (2 × FDC's 29.6 g per fl oz) |
| Instant coffee | 6 fl oz cup (180 ml) | 47 mg | FDC 174130: 26 mg per 100 g × 179 g |
| Decaf brewed coffee | 8 fl oz cup (237 ml) | 2 mg | FDC 171889: 1 mg per 100 g × 237 g |
| Black tea | 8 fl oz cup (237 ml) | 47 mg | FDC 173227: 20 mg per 100 g × 237 g |
| Green tea | 1 cup (245 g) | 29 mg | FDC 171917: 12 mg per 100 g × 245 g |
| Oolong tea | 8 fl oz cup (237 ml) | 38 mg | FDC 174120: 16 mg per 100 g × 237 g (FDC lists no serving; 237 g, as for brewed black tea) |
| Herbal tea (not chamomile) | 8 fl oz cup (237 ml) | 0 mg | FDC 173232: 0 mg per 100 g × 237 g |
| Cola | 12 fl oz can (355 ml) | 33 mg | FDC 174852: 9 mg per 100 g × 370 g |
| Dark chocolate, 70–85% cacao | 1 oz (28 g) | 23 mg | FDC 170273: 80 mg per 100 g × 28.35 g |
- Caffeine per serving: USDA FoodData Central (SR Legacy entries in the table above). Typical ranges for 12 fl oz drinks, 400 mg a day for most adults, and advice for pregnancy, children and teens: Spilling the Beans: How Much Caffeine Is Too Much?, US Food and Drug Administration (content current as of 28 August 2024).
- Under 200 mg a day in pregnancy: Committee Opinion No. 462, Moderate Caffeine Consumption During Pregnancy, American College of Obstetricians and Gynecologists (2010).
- Single doses up to 200 mg and up to 400 mg a day for healthy adults; up to 200 mg a day in pregnancy and while breastfeeding; 3 mg per kg a day for children and adolescents; 100 mg near bedtime and sleep; half-life about 4 hours (range 2–8 hours): EFSA explains risk assessment: Caffeine (2015), summarising the Scientific Opinion on the safety of caffeine, EFSA Journal 2015;13(5):4102.
Questions
How long does caffeine stay in the body?
EFSA gives an average half-life of about 4 hours in healthy adults, with a range of 2 to 8 hours, so half of a morning coffee may still be there in the afternoon. That is why the bedtime figure is shown as a range and labelled a rough estimate.
Is decaf caffeine-free?
Not quite. USDA FoodData Central lists brewed decaf at about 1 mg per 100 g, roughly 2 mg in an 8 fl oz cup, compared with about 95 mg for regular brewed coffee.
Does the calculator save my drinks?
No. The list lives only in this page while it is open and is never sent anywhere; reloading the page brings back the example day.