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A standard 12-ounce Pepsi has slightly more caffeine than a standard 12-ounce Coke: 38 milligrams versus 34 milligrams. That four-milligram difference changes for diet versions, where Diet Coke has 46 milligrams and Diet Pepsi has 35 milligrams per 12 ounces.
At a glance: caffeine in Coke and Pepsi
The fairest comparison uses the same serving size and the same type of product. The current U.S. figures for 12-fluid-ounce servings are:
| Product | Serving | Caffeine | Published by |
|---|---|---|---|
| Coca-Cola (regular) | 12 fl oz | 34 mg | The Coca-Cola Company, current FAQ |
| Pepsi (regular, U.S.) | 12 fl oz | 38 mg | Pepsi, current U.S. FAQ |
| Diet Coke | 12 fl oz | 46 mg | The Coca-Cola Company, current FAQ |
| Diet Pepsi | 12 fl oz | 35 mg | Pepsi, current U.S. FAQ |
For regular cola, Pepsi is higher by 4 milligrams per 12-ounce serving. For diet cola, the order reverses: Diet Coke is higher than Diet Pepsi by 11 milligrams. Those are small differences in absolute terms, but they matter if you are limiting caffeine or drinking several servings.
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Pepsi has the higher listed amount
Pepsi’s U.S. product information states that a 12-ounce can contains 38 milligrams of caffeine. The Coca-Cola Company lists 34 milligrams for a 12-ounce can of Coke. Holding the serving size constant, Pepsi therefore contains about 12 percent more caffeine than Coke (4 milligrams divided by Coke’s 34 milligrams).
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The difference is not large enough to make one can a dramatically stronger stimulant than the other. It is roughly the amount found in a few sips of a caffeinated drink, not a second full serving. If you can notice a difference after switching brands, serving size, total daily intake, sugar, sleep, and individual sensitivity may matter more than those four milligrams.
What the laboratory evidence found
A peer-reviewed study in the Journal of Analytical Toxicology, indexed by PubMed in 2007, tested carbonated beverages with high-performance liquid chromatography. The sample included 56 national-brand drinks and 75 private-label drinks. In that analysis, Coca-Cola measured 33.9 milligrams per 12 ounces and Pepsi measured 38.9 milligrams per 12 ounces. The measured results closely track the companies’ current rounded figures, although a laboratory result from 2007 is not a guarantee that every can sold today has the same formulation.
The study also demonstrates why a label value should be treated as product-specific. It tested particular products available at that time, while recipes, manufacturing locations, and market formulations can change.
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Diet Coke lists more caffeine
Diet Coke contains 46 milligrams per 12 ounces according to The Coca-Cola Company. Diet Pepsi contains 35 milligrams per 12 ounces according to Pepsi’s U.S. FAQ. That makes Diet Coke 11 milligrams higher per equal serving, a much wider gap than the four-milligram difference between regular Coke and regular Pepsi.
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The 2007 laboratory study measured 46.3 milligrams for Diet Coke and 36.7 milligrams for Diet Pepsi. These values point in the same direction as the current label figures. Diet status does not predict caffeine content: removing or reducing sugar does not automatically reduce caffeine.
Do not combine sweetener and caffeine assumptions
Regular, diet, and zero-sugar products use different formulations. A drink can have fewer calories yet contain more caffeine, or have a similar caffeine amount despite a different sweetener. Compare the caffeine declaration and the sugar or calorie panel separately instead of using one as a proxy for the other.
Why serving size changes the answer
A 12-ounce can is the reference point for the figures above. A larger bottle, convenience-store cup, or fountain serving contains proportionally more caffeine if it uses the same recipe and is filled to the stated volume.
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For a simple estimate, multiply the 12-ounce caffeine value by the package volume and divide by 12. On that basis, a 16-ounce serving would contain approximately 45.3 milligrams from regular Coke (34 × 16 ÷ 12) and 50.7 milligrams from regular Pepsi (38 × 16 ÷ 12). The same calculation gives about 61.3 milligrams for Diet Coke and 46.7 milligrams for Diet Pepsi. These are arithmetic estimates, not independent measurements; use the package’s own nutrition information when it provides a serving-specific value.
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Multi-liter bottles create the same issue. If you pour two 12-ounce servings, you consume twice the listed caffeine. A bottle label may define a serving as ocho, 12, or another number of ounces, so check both the serving size and the number of servings per container. Ice displaces liquid in a fountain cup, while an overfilled cup can change the actual amount; the printed serving volume is the reliable starting point.
Country, formulation, and package caveats
The 38-milligram Pepsi figure is explicitly for the United States. Product names can cover different recipes in other countries, and caffeine levels can vary among regular, diet, zero-sugar, cherry, vanilla, limited-edition, and caffeine-free versions. Even within one brand, a can and a fountain beverage may have different labeling or dispensing conditions.
Use the exact label on the product you are buying. The Coca-Cola Company says caffeine information is printed near the Nutrition Facts label. Pepsi says caffeine appears in the ingredient statement and on the product label. If a package does not show a number, look for a manufacturer FAQ for that specific country and product, or choose a clearly labeled caffeine-free version rather than assuming the amount.
- Confirm the full product name, including “Diet,” “Zero Sugar,” flavor, or “Caffeine Free.”
- Check the serving size in fluid ounces or milliliters.
- Multiply by the number of servings you actually plan to drink.
- Read the country-specific label when buying imported or travel-packaged products.
How cola fits within daily caffeine guidance
Health Canada’s 2025 guidance gives an average range of 36 to 46 milligrams for a 12-ounce regular cola and 39 to 50 milligrams for a 12-ounce diet cola. The four products in the table fall within or close to those broad ranges. Health Canada lists 400 milligrams per day as the recommended maximum caffeine intake for adults age 18 and over.
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One 12-ounce can therefore represents only part of that daily maximum. Four regular Pepsi cans would total 152 milligrams based on the listed value; four regular Coke cans would total 136 milligrams. Four Diet Coke cans would total 184 milligrams, while four Diet Pepsi cans would total 140 milligrams. Those totals count only the cola. Coffee, tea, energy drinks, chocolate, medications, and supplements can add substantially more.
The 400-milligram figure is a population-level recommendation, not a personal target or a guarantee that a given amount will feel comfortable. Sensitivity varies, and people may choose lower limits for sleep, anxiety, heart rhythm concerns, medication interactions, pregnancy, or other medical reasons. If caffeine causes symptoms or you have a condition affected by stimulants, ask a clinician for advice tailored to you.
A practical method for comparing any can or bottle
- Match the serving size. Put both products on a 12-ounce basis, or compare the exact volumes you will drink. Comparing a 16-ounce Pepsi with a 12-ounce Coke without adjusting the volume will overstate the recipe difference.
- Match the formulation. Compare regular with regular, diet with diet, and zero-sugar with the same category. Do not infer caffeine from calorie or sugar content.
- Read the product label. Look near the Nutrition Facts panel for Coke and in Pepsi’s ingredient statement or product labeling. Record the milligrams and the serving count.
- Account for the whole container. Multiply caffeine per serving by the number of servings consumed. A bottle that contains two servings can deliver twice the can-sized amount.
- Check the market. For products purchased outside the United States, use that package’s information rather than importing the U.S. number.
- Add your other caffeine. Include coffee, tea, energy drinks, chocolate, and caffeine-containing medicines when considering your daily total.
Common situations and what to expect
If you want the least caffeine among these four products
Regular Coke has the lowest listed amount at 34 milligrams per 12 ounces, followed by Diet Pepsi at 35 milligrams. The one-milligram difference between those two is negligible for most practical purposes, but the labels still place them in that order.
If you want the most caffeine among these four products
Diet Coke is highest at 46 milligrams per 12 ounces. Regular Pepsi follows at 38 milligrams. Choosing a diet or zero-sugar drink does not mean choosing less caffeine.
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If you are switching from regular to diet
Check the caffeine number before assuming the change will lower your intake. Switching from regular Coke to Diet Coke raises the listed caffeine from 34 to 46 milligrams per 12 ounces. Switching from regular Pepsi to Diet Pepsi lowers it from 38 to 35 milligrams. The direction depends on the brand.
If you drink fountain cola
Ask for the serving volume or inspect the restaurant’s nutrition information. Cup size alone can be misleading because ice occupies part of the container, and dispenser calibration and recipe can differ by location. Treat the manufacturer’s package figure as a guide, not a laboratory measurement of every fountain pour.
If you need to avoid caffeine completely
Choose a product explicitly labeled “caffeine free.” Neither regular nor diet status is enough to establish that a drink contains no caffeine. Verify the exact flavor and package because a caffeine-free variant is a separate formulation.
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For one 12-ounce serving, the regular-brand gap is modest: Pepsi supplies 38 milligrams and Coke 34 milligrams. The difference becomes more noticeable only as servings accumulate. After three equal servings, the arithmetic gap is 12 milligrams. After five, it is 20 milligrams. The diet-brand gap accumulates faster because it is 11 milligrams per serving: three servings differ by 33 milligrams.
These calculations assume the same listed values for every serving and do not account for regional or recipe changes. They are useful for planning, but the package in your hand remains the authoritative source for that purchase.
Bottom line
For standard U.S. 12-ounce cans, Pepsi has slightly more caffeine than Coke, 38 milligrams versus 34 milligrams. Among diet versions, Diet Coke has more than Diet Pepsi, 46 milligrams versus 35 milligrams. The differences are small per can but can add up across larger containers or multiple servings. Compare equal volumes, separate caffeine from sugar and calories, and verify the exact label for your country and product variant.
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