PepsiCo
How much caffeine is in Diet Pepsi?
Data checked against the source on 2026-10-03 by Oleksii Y.
One 12 fl oz can (360 ml) of Diet Pepsi has 35 mg of caffeine, according to PepsiCo Product Facts.
How Diet Pepsi compares
- Strength: 9.7 mg per 100 ml.
- One 12 fl oz can (360 ml) has as much caffeine as about a quarter to a third of a cup of brewed coffee, which has 94.8 mg per 8 fl oz cup.
- Of the 22 other sodas in our soda chart, 9 have more caffeine per serving and 13 have less.
How much will be left at bedtime?
1 × 12 fl oz can (360 ml) of Diet Pepsi
Left at 11:00 PM (8 h later), average metabolism
≈ 12 mg
Range 6–18 mg (fast to slow metabolism)
35 mg is already at or under the 50 mg this tool aims to have left at bedtime.
What sleep studies found near this dose
- Gardiner et al. 2025 (randomized trial): In 23 healthy young men, 100 mg taken 12, 8 or 4 hours before bed had no significant effect on measured or self-rated sleep.
- Gardiner et al. 2023 (meta-analysis): To avoid losing sleep time, the authors suggest a coffee (107 mg per 250 ml) at least 8.8 hours before bed.
Estimate from a simple model: half-life of 3, 5 or 8 hours, 50 mg bedtime target. How we calculate
How long does Diet Pepsi stay in your system?
Our model halves caffeine every 5 hours for average metabolism, and every 3 or 8 hours for fast or slow metabolism. From one 12 fl oz can (360 ml) of Diet Pepsi (35 mg), about 18 mg is still in your body 5 hours later and about 9 mg after 10 hours. If you clear caffeine slowly (an 8-hour half-life), about 15 mg is left after 10 hours.
Estimated caffeine left at 11:00 PM from one 12 fl oz can (360 ml) (35 mg), using a half-life of 5 hours for average metabolism and 3 to 8 hours for the range. How we calculate
| Had at | Left at bedtime (average) | Range |
|---|---|---|
| 8:00 AM (15 h before bed) | ≈ 4 mg | 1–10 mg |
| 12:00 PM (11 h before bed) | ≈ 8 mg | 3–13 mg |
| 3:00 PM (8 h before bed) | ≈ 12 mg | 6–18 mg |
| 6:00 PM (5 h before bed) | ≈ 18 mg | 11–23 mg |
How many fit in a day?
Reference amounts are for caffeine from all sources combined. Counted at the upper end of the stated amount, one serving at a time:
- Up to 400 mg a day for most healthy adults (FDA, EFSA): about 11 servings.
- Up to 200 mg at one time for healthy adults (EFSA): about 5 servings in one go.
- Up to 200 mg a day in pregnancy (EFSA, NHS): about 5 servings.
These are reference amounts for groups of people, not a personal limit. Some people feel jittery or sleep worse on much less. See the cutoff calculator for timing.
Good to know
Diet Pepsi lists slightly less caffeine than regular Pepsi, which has 38 mg per 12 fl oz can.
Diet Pepsi vs other Pepsi drinks
- Pepsi: Diet Pepsi has less caffeine than Pepsi per 12 fl oz can (360 ml): 35 mg vs 38 mg.
- Pepsi Zero Sugar: Diet Pepsi has less caffeine than Pepsi Zero Sugar per 12 fl oz can (360 ml): 35 mg vs 38 mg.
Common questions
How much caffeine is in Diet Pepsi?
PepsiCo Product Facts gives 35 mg of caffeine per 12 fl oz can (360 ml).
How many Diet Pepsi servings can I have in a day?
The FDA and EFSA cite up to 400 mg of caffeine a day, from all sources combined, for most healthy adults. At 35 mg per 12 fl oz can (360 ml), that is about 11 servings if Diet Pepsi is your only source. In pregnancy the reference is 200 mg a day.
How late can I drink Diet Pepsi?
One serving has about 35 mg, which is at or under the 50 mg our calculator aims to have left at bedtime, so it sets no cutoff for a single serving. Several servings add up.
Does Diet Pepsi have more caffeine than Pepsi?
Diet Pepsi has less caffeine than Pepsi per 12 fl oz can (360 ml): 35 mg vs 38 mg.
How long does Diet Pepsi stay in your system?
Of the 35 mg in one 12 fl oz can (360 ml), roughly 18 mg remains after 5 hours and 9 mg after 10 hours with our average 5-hour half-life. From fast to slow metabolism, 10 hours later it is between 3 and 15 mg.
Where the number comes from
- Diet Pepsi - 12 fl oz (ready to drink). PepsiCo Product Facts. Nutrition facts: "Serving Size 12 fl oz (360 mL)", "Caffeine 35mg" Accessed 2026-10-02. Source ↗
- Pepsi - 12 fl oz. PepsiCo Product Facts. GTIN 00012000000133, nutrition facts: Serving Size 1 can, "Caffeine 38mg" Accessed 2026-10-02. Source ↗
Recipes and labels change. If a number here no longer matches the label, the label wins.
General information, not medical advice
If you feel unwell after caffeine — for example chest pain, a fast or irregular heartbeat that does not settle, fainting, confusion or trouble breathing — get urgent medical help. If you are pregnant or breastfeeding, under 18, take medication, or have a heart, liver or anxiety condition, high blood pressure or a sleep disorder, ask a doctor or pharmacist what amount is right for you.
Sources
- U.S. Food and Drug Administration (2024). Spilling the Beans: How Much Caffeine is Too Much? FDA Consumer Updates. fda.gov ↗
- European Food Safety Authority. Caffeine | EFSA. EFSA topic page (summary of the 2015 Scientific Opinion on the safety of caffeine). efsa.europa.eu ↗
- NHS. Foods to avoid in pregnancy. NHS. nhs.uk ↗
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