Pepsi vs Diet Pepsi vs Diet Coke: which has more caffeine?

Diet Coke has the most caffeine of the three at 46mg per 12 oz can, Pepsi sits in the middle at 38mg, and Diet Pepsi has the least at 35mg. The servings are identical, so the per-can numbers settle it outright: a 11mg spread from top to bottom.

Pepsi vs Diet Pepsi vs Diet Coke: the numbers

Sources: Pepsi is 38mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Pepsi guide; Diet Pepsi is 35mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Diet Pepsi guide; Diet Coke is 46mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Diet Coke guide.

What a 11mg spread actually feels like

All three come in the same 12 oz can, so the gap is the whole difference. 11mg is less than half a cup of brewed coffee, which is the easiest way to size it if you already know your coffee tolerance. Switching from Diet Pepsi to Diet Coke once a day changes your weekly intake by about 77mg.

The three head-to-head pages

Each pairing has its own page with the full math:

• Pepsi vs Diet Pepsi, head to head
• Pepsi vs Diet Coke, head to head
• Diet Pepsi vs Diet Coke, head to head

Which one should you pick?

Take Diet Pepsi when you want the smallest dose of the three, Pepsi when you want a middle number without thinking about it, and Diet Coke when you actually want the 46mg and know how you handle it. If you drink more than one caffeinated thing a day, the useful move is adding the day up against the 400mg reference rather than judging each drink alone.

For context, the FDA cites 400mg of caffeine a day as an amount generally not associated with negative effects in healthy adults. Tolerance and health vary, so treat these numbers as information, not advice.

Related reading

• The verified caffeine database
• Every drink compared: the comparisons index
• Compare any two of 120+ drinks

FAQ

Which has the most caffeine, Pepsi, Diet Pepsi or Diet Coke? Diet Coke, at 46mg per 12 oz can. Pepsi has 38mg per 12 oz can and Diet Pepsi has 35mg per 12 oz can.

Which of the three is strongest per ounce? Diet Coke, at about 3.8mg per fluid ounce, ahead of Pepsi at 3.2mg and Diet Pepsi at 2.9mg.

How many Diet Coke servings reach the FDA 400mg reference? About 8.7 of them, at 12 oz can each. The FDA cites 400mg a day as an amount generally not associated with negative effects in healthy adults. This is information, not advice.