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Cold brew coffee before bed: 155 mg of caffeine and how long it lasts
Updated October 5, 2026 · Sources: DozeClock · U.S. Department of Agriculture · U.S. Food and Drug Administration · National Academies Press
Short answer
155 mg
per 12 fl oz (355 ml)
13 h 10 min
until under 25 mg is left
A 12 fl oz cold brew needs about 13 hours to fall under 25 mg. Order the 16 fl oz size and it climbs past 15 hours.
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.
Model: remaining = dose × 0.5^(hours ÷ 5). Half-life 5 h (Institute of Medicine 2001); real half-lives run 1.5–9.5 h between people.
Of the 155 mg, about 78 mg is left after 5 hours, 39 mg after 10 and 19 mg after 15. That long tail is the point: a mid-afternoon cold brew is still carrying roughly a small cup of coffee at bedtime. The model uses a 5-hour half-life for an average adult, and real half-lives run from 1.5 to 9.5 hours, so a slow metabolizer can sit well above the line.
01Last cold brew coffee by bedtime
| Bedtime | Finish by (25 mg left) | Left at lights out if finished 6 h before | Left if finished 3 h before |
|---|---|---|---|
| 9:00 pm | 7:50 am | 67 mg | 102 mg |
| 9:30 pm | 8:20 am | 67 mg | 102 mg |
| 10:00 pm | 8:50 am | 67 mg | 102 mg |
| 10:30 pm | 9:20 am | 67 mg | 102 mg |
| 11:00 pm | 9:50 am | 67 mg | 102 mg |
| 11:30 pm | 10:20 am | 67 mg | 102 mg |
| 12:00 am | 10:50 am | 67 mg | 102 mg |
| 12:30 am | 11:20 am | 67 mg | 102 mg |
| 1:00 am | 11:50 am | 67 mg | 102 mg |
Finish-by times are rounded down to 5 minutes. 25 mg is this site's planning line, not a clinical threshold. Every drink at once: caffeine cutoff grid.
02Why cold brew runs 100 to 200 mg
Cold brew is steeped in cold water for many hours and then served over ice, sometimes diluted from a concentrate. None of the free government sources fetched for this page list cold brew by name, so the 155 mg on this page is the site figure for a 12 fl oz serving, with a 100 to 200 mg range.
The useful translation is strength per 100 g. Dividing 155 mg by the 355 g of a 12 fl oz serving gives about 44 mg per 100 g, and the 100 to 200 mg range becomes 28 to 56. USDA measures hot brewed coffee at 40 mg per 100 g, with a measured spread of 30 to 44. So cold brew, on this reading, is ordinary-strength coffee sold in a bigger glass.
Size does most of the work. At 12.9 mg per fl oz, a 16 fl oz cup holds about 207 mg and a 20 fl oz cup about 258 mg, which moves the finish-by time earlier by roughly 2 and 4 hours. The 16 fl oz cup is also past the 200 mg mark where this site starts calling a dose large.
Concentrate is the other variable, and it cuts both ways. If a bottle is meant to be mixed one part concentrate to one part water, the concentrate itself would run about twice the strength, near 310 mg per 12 fl oz undiluted. That is arithmetic for illustration, not a measured product. Pour it straight, or skip the water, and you can double a dose without changing cup size.
| Serving or brew | Caffeine | Basis | Source |
|---|---|---|---|
| 12 fl oz cold brew (headline figure) | 155 (100–200) | Figure and range stored in the DozeClock caffeine data | DozeClock data |
| Strength implied by 155 mg, per 100 g | 44 | 155 mg divided by 355.2 g (12 × 29.6 g per fl oz), calculated by DozeClock | USDA FDC 171890 |
| Hot brewed coffee, per 100 g | 40 (30–44) | USDA measured value, 8 data points | USDA FDC 171890 |
| 8 fl oz at the same strength | 103 | 12.9 mg per fl oz × 8, calculated by DozeClock | USDA FDC 171890 |
| 16 fl oz at the same strength | 207 | 12.9 mg per fl oz × 16; about 15 h 15 min to fall under 25 mg, calculated by DozeClock | USDA FDC 171890 |
| 20 fl oz at the same strength | 258 | 12.9 mg per fl oz × 20; about 16 h 50 min to fall under 25 mg, calculated by DozeClock | USDA FDC 171890 |
| 12 fl oz, regular brewed coffee (hot) | 113–247 | FDA consumer update, per 12 fl oz serving | FDA |
Per-size values scale the site figure linearly and are calculated by DozeClock; they are not measured values for those sizes. No brand label was used. The concentrate example is hypothetical arithmetic.
03Cold brew coffee next to the three nearest drinks
| Drink | Serving | mg | Hours to under 25 mg | Finish by for an 11 pm bed |
|---|---|---|---|---|
| Energy shot | 2 fl oz (60 ml) | 200 | 15 h | 8:00 am |
| Cold brew coffee | 12 fl oz (355 ml) | 155 | 13 h 10 min | 9:50 am |
| Brewed coffee | 8 fl oz (237 ml) | 96 | 9 h 42 min | 1:15 pm |
| Energy drink | 8 fl oz (237 ml) | 72 | 7 h 38 min | 3:20 pm |
mg per serving, not per ounce: servings differ in size · nearest = smallest difference in mg per serving (data/caffeine.json)
Cold brew is the largest standard coffee serving in the data, which is why it ranks above hot brewed coffee here despite similar strength per gram. The long tail matters more than the headline: 155 mg leaves close to 13 hours on the clock. If you want the flavor late, a small size or a decaf pour is the closest swap.
Sources
- DozeClock caffeine data: cold brew coffee, 12 fl oz, 155 mg, range 100–200 mg (data/caffeine.json, attributed there to USDA FoodData Central; not re-verifiable on a single USDA page) — DozeClock
- FoodData Central: Beverages, coffee, brewed, prepared with tap water (SR Legacy, FDC ID 171890) — U.S. Department of Agriculture
- Spilling the Beans: How Much Caffeine is Too Much? — U.S. Food and Drug Administration
- 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.