Caffeine Calculator: How Long Until It Wears Off?
Caffeine has a half-life of 5-6 hours. A 200mg coffee at 2:00 PM leaves approximately 100mg in your system at 8:00 PM and 50mg at 2:00 AM. For healthy sleep, stop caffeine intake 8-10 hours before bedtime. FDA safe limit: 400mg/day for healthy adults (about 4 cups of coffee).
Caffeine Calculator
See when caffeine wears off based on half-life decay.
Caffeine at Bedtime
--
--
Caffeine Content of Common Drinks
| Drink | Serving | Caffeine | |||
|---|---|---|---|---|---|
| Drip coffee | 8 oz | 95mg | |||
| Drip coffee | 16 oz (grande) | 190mg | |||
| Espresso | 1 shot (1 oz) | 63mg | |||
| Cold brew | 16 oz | 200mg | |||
| Black tea | 8 oz | 47mg | |||
| Green tea | 8 oz | 28mg | |||
| Diet Coke | 12 oz | 46mg | |||
| Red Bull | 8.4 oz | 80mg | |||
| Monster Energy | 16 oz | 160mg | |||
| Pre-workout (typical) | 1 scoop | 150-300mg | |||
| Caffeine pill | 1 pill | 200mg | |||
| Dark chocolate | 1 oz | 12mg | |||
| Decaf coffee | 8 oz | 2-15mg | Caffeine Half-Life Breakdown | Hours After Intake | Caffeine Remaining (from 200mg) |
| 0 hours | 200mg (100%) | ||||
| 3 hours | 141mg (71%) | ||||
| 5 hours | 100mg (50%) | ||||
| 10 hours | 50mg (25%) | ||||
| 15 hours | 25mg (13%) | ||||
| 20 hours | 13mg (6%) |
Factors That Affect Caffeine Metabolism
- Genetics: CYP1A2 gene variants make you a fast or slow metabolizer
- Pregnancy: Half-life doubles to 10-12 hours (limit 200mg/day)
- Smoking: Speeds metabolism by ~50% (shorter half-life)
- Oral contraceptives: Slow metabolism by ~30%
- Liver disease: Significantly slows metabolism
- Age: Metabolism slows with age
Frequently Asked Questions
How long does caffeine stay in your system?
Caffeine has a half-life of approximately 5-6 hours in healthy adults, meaning half the caffeine is eliminated every 5-6 hours. It takes about 10-12 hours for 75% to be cleared. However, individual metabolism varies widely — genetic fast metabolizers (CYP1A2 gene) may clear caffeine in 3-4 hours, while slow metabolizers may take 8+ hours. Caffeine sensitivity also varies independently of metabolism speed.
How much caffeine is too much?
The FDA recommends a maximum of 400mg per day for healthy adults (approximately 4 cups of coffee). The European Food Safety Authority also sets 400mg as the safe upper limit. Above 600mg, adverse effects become common: anxiety, insomnia, heart palpitations, and digestive issues. During pregnancy, limit to 200mg/day (WHO/ACOG recommendation). Children and adolescents should limit to 100mg/day.
When should I stop drinking caffeine for good sleep?
Stop caffeine intake at least 8-10 hours before your target bedtime. A 2013 study in the Journal of Clinical Sleep Medicine found that caffeine consumed 6 hours before bedtime still reduced total sleep time by over 1 hour. If you go to bed at 10:00 PM, your last caffeine should be before 12:00-2:00 PM. If you are caffeine-sensitive, you may need to stop even earlier.
Does caffeine tolerance reduce its effects?
Regular caffeine consumption does build tolerance to its alerting effects within 1-2 weeks — you need more to feel the same 'boost.' However, tolerance to caffeine's sleep-disrupting effects is incomplete. Even habitual coffee drinkers who do not feel stimulated by evening coffee show measurable reductions in sleep quality and deep sleep in EEG studies.
Is caffeine addictive?
Caffeine produces physical dependence (withdrawal symptoms include headache, fatigue, irritability, and difficulty concentrating) but is not classified as an addictive substance by most medical authorities. Withdrawal symptoms typically begin 12-24 hours after last intake, peak at 20-51 hours, and resolve within 2-9 days. Tapering by 25% every 2-3 days minimizes withdrawal.