Coca-Cola Classic vs Diet Coke vs Coca-Cola Zero Sugar: which has more caffeine?

Diet Coke has the most caffeine of the three at 46mg per 12 oz can, Coca-Cola Classic sits in the middle at 34mg, and Coca-Cola Zero Sugar has the least at 34mg. The servings are identical, so the per-can numbers settle it outright: a 12mg spread from top to bottom.

Coca-Cola Classic vs Diet Coke vs Coca-Cola Zero Sugar: the numbers

Sources: Coca-Cola Classic is 34mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Coca-Cola Classic guide; Diet Coke is 46mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Diet Coke guide; Coca-Cola Zero Sugar is 34mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our the caffeine database.

What a 12mg spread actually feels like

All three come in the same 12 oz can, so the gap is the whole difference. 12mg 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 Coca-Cola Zero Sugar to Diet Coke once a day changes your weekly intake by about 84mg.

The three head-to-head pages

Each pairing has its own page with the full math:

• Coca-Cola Classic vs Diet Coke, head to head
• Coca-Cola Classic vs Coca-Cola Zero Sugar, head to head
• Diet Coke vs Coca-Cola Zero Sugar, head to head

Which one should you pick?

Take Coca-Cola Zero Sugar when you want the smallest dose of the three, Coca-Cola Classic 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, Coca-Cola Classic, Diet Coke or Coca-Cola Zero Sugar? Diet Coke, at 46mg per 12 oz can. Coca-Cola Classic has 34mg per 12 oz can and Coca-Cola Zero Sugar has 34mg per 12 oz can.

Which of the three is strongest per ounce? Diet Coke, at about 3.8mg per fluid ounce, ahead of Coca-Cola Classic at 2.8mg and Coca-Cola Zero Sugar at 2.8mg.

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.