Caffeine Intake Calculator
Calculate your total daily caffeine intake from coffee, tea, and energy drinks. Find your safe limit and recommended cutoff time. Evidence-based, free, instant.
All calculations run instantly in your browser. No data is sent to any server.
Disclaimer: Results are for informational purposes only and do not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare professional for personal guidance.
Caffeine and Sleep Quality
Caffeine works by blocking adenosine receptors — adenosine is the chemical that builds up during wakefulness and promotes sleep drive. Caffeine doesn't destroy adenosine; it merely masks it. When caffeine is metabolised, the accumulated adenosine floods the receptors, often causing a rebound fatigue that drives the next caffeine intake. Matthew Walker's research shows that even with subjective alertness restored, caffeine meaningfully reduces deep (slow-wave) sleep even when consumed 6 hours before bedtime.
Caffeine Reference Guide
| Drink | Caffeine |
|---|---|
| Espresso shot (30ml) | 60–65mg |
| Filter/drip coffee (240ml) | 95–100mg |
| Black tea (240ml) | 45–50mg |
| Energy drink (250ml) | 80mg |
| Cola (330ml) | 35–40mg |
FAQs
How much caffeine is safe?
Up to 400mg/day for healthy adults (FDA). Pregnant: 200mg max. Highly individual — some experience issues at lower doses.
How long does caffeine last?
Half-life 5–6 hours. Coffee at 3pm means 50% still circulating at 8–9pm. Morning coffee can affect sensitive sleepers.
When should I stop drinking caffeine?
At least 6 hours before sleep. For sensitive individuals or those with sleep problems, noon is the recommended cutoff.