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Caffeine Cutoff Calculator

When should you stop drinking coffee to sleep well tonight? Enter your details and get a science-backed cutoff time with a real-time caffeine decay chart.

30 seconds Drake et al., 2013 Peer-reviewed formula

Your details

1
Total: 95 mg caffeine
5.0 hrs
Average is 5 hrs. Slower if pregnant (8–12 hrs) or on birth control (6–7 hrs). Faster if you smoke (3 hrs).
Your last safe coffee is at
5:08
PM
That's 5.9 hrs before bedtime. You'll have ~22 mg in your system when you go to sleep.
23%
caffeine remaining at bedtime
1.2
half-lives before bed
~14h
to fully clear (<5 mg)

Caffeine decay over time

Sleep impact assessment

The science behind this calculator

Caffeine blocks adenosine receptors in your brain — the molecule that builds up sleep pressure during the day. Even when you feel "fine" after afternoon coffee, measurable caffeine remains in your system and can reduce deep sleep quality by up to 20%.

This calculator uses exponential decay, the standard pharmacokinetic model for caffeine metabolism:

C(t) = C₀ × (0.5)t / t½
C₀ = starting caffeine (mg) · t = hours elapsed · t½ = half-life (default 5 hrs)

The cutoff time is calculated by working backward from your bedtime to find when caffeine drops below 25 mg — the threshold below which most adults experience negligible sleep disruption.

DrinkServingCaffeine
Drip coffee8 oz95 mg
Espresso1 shot63 mg
Cold brew12 oz200 mg
Black tea8 oz47 mg
Green tea8 oz28 mg
Coca-Cola12 oz34 mg
Red Bull8.4 oz80 mg
Monster16 oz160 mg
Drake, C., Roehrs, T., Shambroom, J., & Roth, T. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine, 9(11), 1195–1200.