How much caffeine is in a Coke?
34 mg in a 12 oz can of Coca-Cola and 46 mg in a can of Diet Coke, by Coca-Cola’s own numbers. That’s a third to a half of an 8 oz brewed coffee, which has about 95 mg.
Diet Coke has more caffeine than regular Coke, about a third more. A lot of people guess the other way, since “diet” sounds like the lighter version of everything.
We think one can in the afternoon is a small dose, regular or diet. A Coke at 3pm leaves about 12 mg in you at an 11pm bedtime, and a Diet Coke about 17. Even a can with dinner at 7pm leaves about 22 mg, or 29 for Diet Coke, both under the lower of our two bedtime lines (40 mg).
Coke against coffee
Coca-Cola makes the comparison itself. Its FAQ says a 12 oz coffee “has 140mg or more”, about four times a can of Coke.
| Drink | Caffeine | Left at 11pm from a 3pm drink | From a 7pm drink |
|---|---|---|---|
| Coca-Cola, 12 oz | 34 mg | 12 mg | 22 mg |
| Diet Coke, 12 oz | 46 mg | 17 mg | 29 mg |
| Black tea, 8 oz | 47 mg | 17 mg | 30 mg |
| Brewed coffee, 8 oz | 95 mg | 35 mg | 60 mg |
These use the average half-life of 5 hours.
A can of Coke as a unit
A can of Coke is a handy picture for a small amount of caffeine. The cutoff clock and the quiz use it that way. Falling asleep with about a can of Coke’s worth in you (15 to 40 mg) is in our low band. An 8 oz coffee at 3pm gets you there by 11pm, at about 35 mg.
Coke and kids
Pediatricians suggest at most 100 mg of caffeine a day for ages 12 to 18, and advise against routine caffeine under 12, according to the American Academy of Child and Adolescent Psychiatry’s 2026 sheet. The sheet puts 100 mg at “about two 12 oz cans of cola”. With Coca-Cola’s numbers, two cans of Coke are 68 mg and two Diet Cokes are 92 mg, both inside it (caffeine for teenagers).
A Coke after dinner
If a soda with dinner is your habit, regular Coke is the smaller dose of the two. If you’d rather have none, a caffeine-free version is the swap. Try your evening in the cutoff clock below.
34 mg
Coca-Cola, 12 oz can. The Coca-Cola Company: 34 mg in a 12 oz can. One at 3pm still leaves about 12 mg at an 11pm bedtime.
When should I stop?
When you fall asleep at 11:00pm
83 mgA measured cost
You'll fall asleep with about a cup of coffee in you.
- Brewed coffee, 8 oz95 mg
Brewed coffee, 16 oz190 mg
Your last drink, a 16 oz coffee at 3:00pm
- Under 40 mg at sleep
- by 8:10am
- Under 80 mg
- by 2:45pm
The full clock, with the band, 3am and the table by drink.
4 sources
- The Coca-Cola Company, What is caffeine? checked 2026-11-14coca-colacompany.com
- USDA FoodData Central, SR Legacy: brewed coffee (171890), espresso (171891), brewed black tea (173227) and brewed green tea (171917)fdc.nal.usda.gov
- American Academy of Child and Adolescent Psychiatry, Facts for Families No. 131: Caffeine and Children, April 2026aacap.org
- Antonio J and others, Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 2024doi.org
