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Caffeine cutoff for a 9:30 pm bedtime: when to have your last coffee
Updated October 3, 2026 · Sources: Drake 2013 · FDA · IOM 2001 · USDA
Short answer
3:30 pm
is six hours before a 9:30 pm bedtime — the latest point the trial evidence supports for a full-strength coffee.
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.
If lights go out at 9:30 pm, the six-hour line falls at 3:30 pm. In the 2013 trial behind that number, a 400 mg dose at that point cut total sleep by over an hour without people feeling it. Using the 5-hour half-life, a 96 mg coffee at 3:30 pm is down to roughly 42 mg by 9:30 pm. Drink it at 6:30 pm instead and 63 mg is still circulating.
Half-life varies from about 1.5 to 9.5 hours between people — smokers clear caffeine faster, pregnancy and some medicines slow it down — so the table below is a model, not a measurement of you. The FDA's own range is 4 to 6 hours.
Half-life 5 h; shaded = FDA 4–6 h · as of October 3, 2026
Last-cup times by drink for a 9:30 pm bedtime
"Under 25 mg" is the illustrative line used across this site — roughly a quarter of a cup of coffee — not a clinical threshold. Each row shows when you would need to finish the drink for its caffeine to fall below that line by 9:30 pm, at the average 5-hour half-life.
| Drink | Caffeine | Hours to < 25 mg | Finish by | Left if at 3:30 pm |
|---|---|---|---|---|
| Energy shot | 200 mg | 15.0 h | 6:30 am | 87 mg |
| Cold brew coffee | 155 mg | 13.2 h | 8:20 am | 67 mg |
| Brewed coffee | 96 mg | 9.7 h | 11:48 am | 42 mg |
| Energy drink | 72 mg | 7.6 h | 1:52 pm | 31 mg |
| Matcha (1 tsp powder) | 70 mg | 7.4 h | 2:04 pm | 30 mg |
| Espresso | 64 mg | 6.8 h | 2:43 pm | 28 mg |
| Instant coffee | 62 mg | 6.6 h | 2:57 pm | 27 mg |
| Black tea | 47 mg | 4.6 h | 4:57 pm | 20 mg |
| Cola | 33 mg | 2.0 h | 7:30 pm | 14 mg |
| Green tea | 28 mg | 0.8 h | 8:41 pm | 12 mg |
| Dark chocolate | 24 mg | 0 h | any time | 10 mg |
| Decaf coffee | 2 mg | 0 h | any time | 1 mg |
remaining = dose × 0.5^(hours ÷ 5) · drinks: FDA, USDA, Mayo Clinic figures · methodology
Sources
- Caffeine content for coffee, tea, soda and more — Mayo Clinic
- Spilling the Beans: How Much Caffeine is Too Much? — U.S. Food and Drug Administration
- FoodData Central — U.S. Department of Agriculture
- Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed — J Clin Sleep Med 9(11):1195-1200, 2013 (Drake C. et al.)
- Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations — National Academies Press, 2001
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.