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Caffeine Decay & Cutoff Calculator

Caffeine has an average half-life of 5 to 7 hours. Calculate your exact biological cutoff to ensure under 50mg of active caffeine remains in your system at bedtime.

Or Quick-Select from Database

Last Safe Coffee Cutoff

05:00 PM

Calculated to ensure you have under 50mg of active circulating caffeine by bedtime, preserving deep slow-wave sleep.

Stop guessing your cutoff.

The ARC app recalculates your cutoff time dynamically with every sip, displaying your live decay curve and lock screen notifications.

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<iframe src="https://arcapp.sbs/tools/caffeine-calculator" width="100%" height="600px" frameborder="0"></iframe>

The Science Behind the Calculator

Caffeine operates like a pharmaceutical with a specific half-life, typically around 5 to 7 hours for a healthy adult. This means 6 hours after you finish your coffee, exactly half of the caffeine is still active in your bloodstream, blocking adenosine receptors and preventing restorative deep sleep.

Why is my cutoff time so early?

To achieve high-quality sleep, your active caffeine levels should ideally be below 25mg at bedtime. If you consume a 200mg energy drink at 3:00 PM, you will still have over 80mg active in your system at 11:00 PM. Our calculator does the exponential decay math for you, ensuring you hit that zero-point exactly when you need to sleep.

How does this affect my Circadian Rhythm?

Caffeine doesn't give you energy; it borrows it from tomorrow. It binds to adenosine receptors (the chemical that makes you feel tired). When the caffeine finally wears off, all that built-up adenosine floods your receptors, causing a crash. Mismanaging this cycle disrupts your core temperature minimum and delays your natural melatonin release, throwing your entire circadian rhythm out of sync.