Coffee, brewed vs Diet Coke: caffeine compared
Coffee, brewed (8 oz) has 95 mg of caffeine, 49 mg more than Diet Coke (12 oz, 46 mg) — 2.1× as much per serving. Per fluid ounce, Coffee, brewed is the stronger drink: 11.9 mg/oz versus 3.8 mg/oz.
| Coffee, brewed | Diet Coke | |
|---|---|---|
| Serving | 8 oz | 12 oz |
| Caffeine per serving | 95 mg | 46 mg |
| Per fl oz | 11.9 mg | 3.8 mg |
| Share of 400 mg/day | 24% | 12% |
| Servings to reach 400 mg | 4.2 | 8.7 |
| Hours until under 50 mg | 4.6 h | already under |
| Last one for an 11 PM bedtime · standard (50 mg) | 6:22 PM | 11:00 PM |
| Last one for an 11 PM bedtime · sensitive (25 mg) | 1:22 PM | 6:36 PM |
| Share of the 200 mg pregnancy limit | 48% | 23% |
One serving of each, over 16 hours
Common questions
Which has more caffeine, Coffee, brewed or Diet Coke?
Coffee, brewed (8 oz) has about 95 mg versus 46 mg in Diet Coke (12 oz): 49 mg more, or 2.1× as much.
Which is stronger per ounce, Coffee, brewed or Diet Coke?
Coffee, brewed: about 11.9 mg per fl oz versus 3.8 mg for Diet Coke. Serving size decides the total you actually drink.
How many Diet Coke servings equal one Coffee, brewed?
About 2.1 servings of Diet Coke (12 oz) match the caffeine in one Coffee, brewed (8 oz).
When should I stop drinking Coffee, brewed or Diet Coke before bed?
For an 11 PM bedtime with a 50 mg limit and a 5-hour half-life: last Coffee, brewed by 6:22 PM, last Diet Coke by 11:00 PM. Half-life varies from about 1.5 to 9.5 hours between people.
Method
Caffeine per labeled serving, from the same drink table every calculator here uses (FDA/USDA reference amounts and manufacturer labels; see caffeine content of every drink). Brewed drinks vary batch to batch, so read these as typical values. Decay uses a 5-hour average half-life with a 45-minute absorption ramp; cutoff = bedtime − 5 h × log₂(dose ÷ limit). Percentages use the FDA's 400 mg/day figure for healthy adults and the 200 mg/day limit ACOG gives for pregnancy.
Source — Coffee, brewed: USDA FoodData Central (SR Legacy 171890), checked 2026-10-13. 40 mg per 100 g × 237 g (8 fl oz).
Source — Diet Coke: Coca-Cola — What is caffeine? (FAQ), checked 2026-10-13.