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Dark chocolate before bed: 24 mg of caffeine and how long it lasts
Updated October 5, 2026 · Sources: U.S. Department of Agriculture · U.S. Food and Drug Administration · National Academies Press
Short answer
24 mg
per 1 oz (28 g)
0 h
already under 25 mg
One ounce of dark chocolate holds about 24 mg, already under this site's 25 mg planning line, so the clock reads zero. The answer changes with the portion: three ounces is 72 mg and about 7 h 40 min, and a whole bar can match a cup of coffee.
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.
24 mg for an ounce is low. The risk is quantity: an ingredient list will not show the caffeine in chocolate, so a late-night half bar is easy to underestimate. Weigh it. Every extra ounce of 60 to 69 percent chocolate adds about 24 mg to the evening total.
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.
After 5 hours about 12 mg of a 24 mg ounce remain, and after 10 hours about 6. The curve only matters once you eat more than one ounce, because the starting point is already under the line. The same model gives 48 mg (two ounces) about 4 h 40 min and 96 mg (a 112 g bar of 60 to 69 percent) about 9 h 40 min. It assumes an average 5 hour half-life, and the measured range is 1.5 to 9.5 hours (Institute of Medicine, 2001).
01Last dark chocolate 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 | any time | 10 mg | 16 mg |
| 9:30 pm | any time | 10 mg | 16 mg |
| 10:00 pm | any time | 10 mg | 16 mg |
| 10:30 pm | any time | 10 mg | 16 mg |
| 11:00 pm | any time | 10 mg | 16 mg |
| 11:30 pm | any time | 10 mg | 16 mg |
| 12:00 am | any time | 10 mg | 16 mg |
| 12:30 am | any time | 10 mg | 16 mg |
| 1:00 am | any time | 10 mg | 16 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.
02Cacao percentage does not rank the caffeine
The USDA has three dark chocolate entries, split by cacao solids. Per 100 g, the 45 to 59 percent bar has 43 mg (measured 40 to 50, 3 data points), the 60 to 69 percent bar 86 mg (70 to 100, 3 data points) and the 70 to 85 percent bar 80 mg (80 to 80, 2 data points). Per ounce that is 12, 24 and 23 mg. The darkest bracket is not the highest here, though with two or three samples per entry, read the order as a hint, not a rule.
Chocolate is rarely eaten by the ounce. USDA lists a bar as 162 g for the 45 to 59 percent entry, 112 g for 60 to 69 and 101 g for 70 to 85. Eating the lot comes to about 70, 96 and 81 mg. The 60 to 69 percent bar lines up with the 96 mg of a brewed cup of coffee, and a label will not warn you: the FDA notes that caffeine does not appear on an ingredient list when it comes from an ingredient such as chocolate chips.
USDA also lists theobromine, a relative of caffeine, in the same entries: 493, 632 and 802 mg per 100 g, which is roughly 140, 179 and 227 mg per ounce. That is 7 to 11 times the caffeine by weight. This page does not model it: no source on how theobromine affects sleep was fetched, so the clock tracks caffeine only.
| Serving or brew | Caffeine | Basis | Source |
|---|---|---|---|
| 1 oz, 45–59% cacao | 12 (11–14) | 43 mg per 100 g, measured range 40–50, 3 data points; multiplied by 28.35 g | USDA FDC 170271 |
| 1 oz, 60–69% cacao (headline figure) | 24 (20–28) | 86 mg per 100 g, measured range 70–100, 3 data points; multiplied by 28.35 g | USDA FDC 170272 |
| 1 oz, 70–85% cacao | 23 (23–23) | 80 mg per 100 g, measured 80–80, 2 data points; multiplied by 28.35 g | USDA FDC 170273 |
| 3 oz, 60–69% cacao, 85 g | 73 (60–85) | Same USDA figures multiplied by 85 g (3 × 28.35 g) | USDA FDC 170272 |
| Whole bar, 45–59% cacao, 162 g | 70 (65–81) | Same USDA figures multiplied by the 162 g bar USDA lists | USDA FDC 170271 |
| Whole bar, 60–69% cacao, 112 g | 96 (78–112) | Same USDA figures multiplied by the 112 g bar USDA lists | USDA FDC 170272 |
| Whole bar, 70–85% cacao, 101 g | 81 (81–81) | Same USDA figures multiplied by the 101 g bar USDA lists | USDA FDC 170273 |
Per-serving values are calculated by DozeClock from USDA mg per 100 g and the gram weights USDA lists (1 oz = 28.35 g; bar weights as shown); they are not measured values for those portions. Theobromine figures are USDA mg per 100 g, converted per ounce by DozeClock.
03Dark chocolate next to the three nearest drinks
| Drink | Serving | mg | Hours to under 25 mg | Finish by for an 11 pm bed |
|---|---|---|---|---|
| Cola | 12 fl oz (355 ml) can | 33 | 2 h | 8:55 pm |
| Green tea | 8 fl oz (237 ml) | 28 | 0 h 49 min | 10:10 pm |
| Dark chocolate | 1 oz (28 g) | 24 | 0 h | any time |
| Decaf coffee | 8 fl oz (237 ml) | 2 | 0 h | any time |
mg per serving, not per ounce: servings differ in size · nearest = smallest difference in mg per serving (data/caffeine.json)
Green tea is 28 mg in 8 fl oz, four more than an ounce of dark chocolate, and cola is 33 mg in a 12 fl oz can. A mug of black tea at 47 mg is matched by about two ounces of 60 to 69 percent chocolate (48 mg). The nearest drink in the data is not a perfect match for an ounce of solid food, so use it as a yardstick and weigh the bar when it matters.
Sources
- FoodData Central: Chocolate, dark, 60-69% cacao solids (SR Legacy, FDC ID 170272; also 170271 and 170273) — 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.