Starbucks Iced Shaken Espresso (Grande) Caffeine Half-Life & Bedtime Decay
A standard Grande Iced Shaken Espresso from Starbucks is built with three shots of espresso (225mg caffeine) shaken vigorously with classic syrup and ice, topped with a splash of milk.
Interactive Stack Calculator for Starbucks Iced Shaken Espresso (Grande)
We've preloaded Starbucks Iced Shaken Espresso (Grande) (225mg) below. Adjust your planned bedtime or add other drinks to see your exact curve.
Caffeine Half-Life & Cutoff Calculator
Caffeine's half-life ranges from about 4 to 7 hours depending on how fast you metabolise it. Add what you've already drunk today to find the last time your next drink still leaves under 50 mg in your system at bedtime.
Caffeine Sensitivity
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Last safe 225 mg drink
For this drink size, the safe window closed earlier today. A smaller drink, or decaf, may still fit.
Today's drinks alone leave about 34 mg at bedtime.
Solid: caffeine from today's drinks.
Stop guessing your cutoff.
Here you type your drinks in. ARC does the same math from every drink you log in one tap, moves your last safe coffee the moment you log a cup, shows it as a live countdown, and tells you plainly when no cup fits any more.
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Starbucks Iced Shaken Espresso (Grande) Hour-by-Hour Caffeine Decay Table
Pharmacokinetic Decay (5.5h Half-Life)Exact milligrams of caffeine remaining in the bloodstream at 2-hour intervals if consumed at various times of day, based on an average human caffeine half-life of 5.5 hours. Target is less than 50mg active at 11:00 PM bedtime.
| Intake Time | +2 hrs | +4 hrs | +6 hrs | +8 hrs | +10 hrs | +12 hrs | At 11 PM Bed | Status |
|---|---|---|---|---|---|---|---|---|
| 08:00 AM | 175 mg | 136 mg | 106 mg | 82 mg | 64 mg | 50 mg | 34 mg | ✓ Sleep Safe |
| 12:00 PM (Noon) | 175 mg | 136 mg | 106 mg | 82 mg | 64 mg | 50 mg | 56 mg | ✕ Above 50mg |
| 02:00 PM | 175 mg | 136 mg | 106 mg | 82 mg | 64 mg | 50 mg | 72 mg | ✕ Above 50mg |
| 04:00 PM | 175 mg | 136 mg | 106 mg | 82 mg | 64 mg | 50 mg | 93 mg | ✕ Above 50mg |
Cutoff Recommendation: Cut off before 1:00 PM for an 11:00 PM sleep target.
Values are calculated using the standard exponential decay model: mg_remaining = initial_mg * 0.5^(hours / half_life).
How Your Genetics (CYP1A2) Impact Starbucks Iced Shaken Espresso (Grande) Clearance
Over 95% of caffeine metabolism takes place in your liver via the cytochrome P450 enzyme CYP1A2. Depending on whether you carry the fast or slow metabolizing gene variant, clearance times for 225mg vary drastically:
Residual after 8 hours: 56 mg. You clear caffeine rapidly and rarely experience insomnia from lunch beverages.
Residual after 8 hours: 82 mg. Standard biological decay rate representing ~50% of the population.
Residual after 8 hours: 102 mg. CYP1A2*1F carriers. Any caffeine consumed past noon will disrupt sleep architecture.
Frequently asked questions
How much caffeine is in an Iced Shaken Espresso?
A Grande contains 3 shots of espresso for 225mg of caffeine. A Venti contains 4 shots delivering 300mg of caffeine.