Pepsi vs Pepsi Zero Sugar: caffeine compared
Pepsi and Pepsi Zero Sugar carry the same caffeine per serving: 38 mg each. Per fluid ounce they are about the same: 3.2 mg/oz versus 3.2 mg/oz.
| Pepsi | Pepsi Zero Sugar | |
|---|---|---|
| Serving | 12 oz | 12 oz |
| Caffeine per serving | 38 mg | 38 mg |
| Per fl oz | 3.2 mg | 3.2 mg |
| Share of 400 mg/day | 10% | 10% |
| Servings to reach 400 mg | 10.5 | 10.5 |
| Hours until under 50 mg | already under | already under |
| Last one for an 11 PM bedtime · standard (50 mg) | 11:00 PM | 11:00 PM |
| Last one for an 11 PM bedtime · sensitive (25 mg) | 7:59 PM | 7:59 PM |
| Share of the 200 mg pregnancy limit | 19% | 19% |
One serving of each, over 16 hours
Common questions
Which has more caffeine, Pepsi or Pepsi Zero Sugar?
Neither: both have about 38 mg per serving.
Which is stronger per ounce, Pepsi or Pepsi Zero Sugar?
About the same: 3.2 mg per fl oz for Pepsi and 3.2 mg for Pepsi Zero Sugar. The difference per can or cup comes from serving size.
When should I stop drinking Pepsi or Pepsi Zero Sugar before bed?
For an 11 PM bedtime with a 50 mg limit and a 5-hour half-life: last Pepsi by 11:00 PM, last Pepsi Zero Sugar 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 — Pepsi: PepsiCo Product Facts — Pepsi 12 fl oz, checked 2026-10-13.
Source — Pepsi Zero Sugar: PepsiCo Product Facts — Pepsi Zero Sugar 12 fl oz, checked 2026-10-13.