Free Caffeine Curfew Calculator 2026 - Find Your Last Safe Coffee Time by Bedtime
Enter your bedtime, drink type and metabolizer speed to instantly calculate your personalised caffeine curfew. Stop caffeine at exactly the right time and protect your deep sleep and sleep score tonight.
Time you plan to go to sleep
Caffeine metabolism rate is determined by CYP1A2 enzyme variants. Slow metabolisers feel effects for 8-10 hours. Fast metabolisers can drink coffee at 5pm and sleep easily.
Common Caffeine Sources
How the Caffeine Curfew Calculator Works
Your caffeine curfew is calculated using pharmacokinetic principles: the caffeine half-life formula combined with a "safe residual threshold" of approximately 25mg - the level below which most people experience minimal sleep disruption. The formula is: Curfew = Bedtime − (log(Total mg / 25) / log(2)) × Half-life in hours.
Step 1: Determine Total Caffeine
We multiply your drink's caffeine content by the number of drinks. Caffeine content varies widely - espresso (63mg/shot) versus a large drip coffee (190mg) versus a pre-workout (200mg) represent very different physiological loads.
Step 2: Apply Your Half-Life
Fast metabolizers (CYP1A2 AA genotype) process caffeine in ~4 hours. Normal metabolizers (AC genotype) take ~5.5 hours. Slow metabolizers (CC genotype) take ~7+ hours. Selecting your type is the most important personalization in the calculator.
Step 3: Calculate Hours Needed
Using logarithmic decay, we calculate how many half-lives are needed to reduce your total dose to ~25mg - the research-based threshold where caffeine has minimal sleep architecture impact.
Step 4: Subtract from Bedtime
The resulting curfew time tells you: "Stop consuming caffeine at or before this time to protect your deep sleep and reduce sleep onset latency tonight."
Caffeine Half-Life by Metabolizer Type
| Type | Half-Life | 200mg Coffee at 2pm | Active at 10pm |
|---|---|---|---|
| Fast (40% of people) | ~4 hours | Curfew: ~11:30am | ~12mg (minimal) |
| Average (majority) | ~5.5 hours | Curfew: ~1:30pm | ~35mg (moderate) |
| Slow (CYP1A2 CC) | ~7 hours | Curfew: ~3:30am (!) | ~71mg (significant) |
Caffeine Content of Popular Drinks
Frequently Asked Questions: Caffeine & Sleep
How does caffeine affect sleep quality?
What is caffeine's half-life and why does it matter?
What factors affect how quickly I metabolize caffeine?
How much caffeine per day is safe?
Can I cancel out caffeine with more sleep?
Does green tea have less sleep impact than coffee?
What about decaf coffee and sleep?
Does caffeine affect everyone's sleep the same way?
What is the best substitute for caffeine before my curfew?
How long after stopping caffeine will my sleep improve?
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