Caffeine Calculator - Daily Intake & Half-Life Tracker
Cooking & Food
Track daily caffeine intake from coffee, tea, energy drinks, and more. See how caffeine levels decline over time using half-life calculations.
Sleep plan
Using a rough 5.5-hour half-life scenario. Metabolism varies with individual biology, pregnancy, smoking, and medicines; these settings are educational examples, not a diagnosis.
The 400 mg/day comparison is the FDA reference for most healthy adults. Individual guidance can differ.
Approximate amount remaining now
≈ 0 mg
Approximate amount at bedtime
Choose a bedtime
Latest modeled time for one additional 95 mg coffee
Choose a bedtime to calculate this estimate.
This model estimate uses the selected half-life and 50 mg user-selected heuristic. It is not a medical recommendation or a guarantee of sleep.
How to use this tool
- Add drinks from the preset list or choose Custom dose to enter caffeine from 0 to 2000 mg per serving. Set each serving count and its local consumed date and time.
- Choose a local bedtime, a user-selected sleep-planning threshold, and a rough half-life scenario. Custom half-life values range from 1 to 24 hours.
- Review approximate caffeine remaining now and at bedtime, plus a model-estimated latest time for one additional 95 mg coffee. These are educational estimates, not medical advice or a guarantee of sleep.
Caffeine content reference
| Drink / food | Serving size | Approx. caffeine |
|---|---|---|
| Espresso (single shot) | 30 mL (1 fl oz) | ~65 mg |
| Drip coffee | 240 mL (8 fl oz) | ~95–200 mg |
| Cold brew coffee | 240 mL | ~150–240 mg |
| Black tea | 240 mL | ~40–70 mg |
| Green tea | 240 mL | ~20–45 mg |
| Matcha | 240 mL (2 tsp powder) | ~70–140 mg |
| Energy drink (standard) | 240–480 mL | ~80–150 mg |
| Cola (12 fl oz) | 355 mL | ~30–45 mg |
| Dark chocolate (1 oz) | 28 g | ~20–25 mg |
Caffeine half-life
Caffeine has an average half-life around 5–6 hours for many adults, but individual metabolism varies. The calculator uses rough educational scenarios: Faster (4 hours), Average (5.5 hours), Slower (8 hours), Pregnancy (15 hours), or a custom value from 1 to 24 hours. These settings do not identify anyone’s genes or medical status. Smoking, pregnancy, oral contraceptives, and some medicines can affect caffeine metabolism, and the actual value can differ from every scenario shown.
Caffeine sensitivity factors
A simplified half-life model estimates what remains from each logged drink. For a dose of 95 mg consumed 5.5 hours ago, the model estimates 47.5 mg remaining at the average setting. For several drinks, it calculates each amount separately and adds the results: a current 95 mg coffee plus another 95 mg coffee consumed 5.5 hours earlier gives 142.5 mg modeled at the current time. The amount is an estimate of caffeine remaining based on time and a selected half-life, not a blood measurement.
Other factors that affect caffeine metabolism include smoking (speeds it up), pregnancy (significantly slows it, half-life up to 15 hours), oral contraceptives (slows it), and certain medications (fluvoxamine, ciprofloxacin). The calculator’s faster, average, slower, and pregnancy settings are only broad scenarios; they are not a genetic or medical diagnosis.
Daily reference amounts
- Most healthy adults: up to 400 mg/day (FDA reference)
- Pregnancy: below 200 mg/day is a moderate-intake comparison in ACOG guidance; it is not a guaranteed safe level
- Children (4–12 years): no established safe level; Health Canada suggests no more than 2.5 mg/kg/day
- Adolescents (13–18 years): no more than 100 mg/day (Health Canada)
Caffeine and sleep quality
Even when caffeine does not prevent sleep onset, it measurably degrades sleep architecture. A sleep study found effects on sleep after caffeine consumed six hours before bedtime, but it does not establish a universal caffeine amount that guarantees good sleep. The bedtime amount and latest-time outputs combine your logged doses, selected half-life, bedtime, and a user-selected 0, 25, 50, or 100 mg threshold. That threshold is only a planning heuristic. Any cutoff time is a model estimate, not a medical recommendation or guarantee of sleep. Decaf coffee can still contain caffeine and may matter to sensitive individuals.
Frequently asked questions
What daily caffeine limit does the tool compare against?
The FDA says up to 400 mg/day is not generally associated with negative effects for most healthy adults. Pregnancy has different guidance; an amount below 200 mg/day is a comparison, not a guarantee of safety.
What is caffeine half-life?
Caffeine has a half-life of about 5–6 hours. This means half the caffeine is metabolized after that time.
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