Regular Pepsi has slightly more caffeine than regular Coke in a 12-ounce serving. Pepsi lists 38 milligrams (mg), while Coca-Cola lists 34 mg—a difference of 4 mg per can.
The result reverses for diet versions: Diet Coke lists 46 mg per 12 ounces, compared with 35 mg for Diet Pepsi. Those figures apply to the cited U.S. products and equal serving sizes; recipes, package sizes and markets can differ, so check the label on the exact drink you buy.
As an Amazon Associate I earn from qualifying purchases.
The caffeine amounts at a glance
Comparing the same 12-fluid-ounce serving keeps the answer fair. The manufacturers’ current figures are:
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
| Product | Serving | Caffeine | What the figure represents |
|---|---|---|---|
| Coca-Cola (regular) | 12 fl oz | 34 mg | The Coca-Cola Company’s current FAQ figure |
| Pepsi (regular, United States) | 12 fl oz | 38 mg | Pepsi’s current U.S. FAQ figure |
| Diet Coke | 12 fl oz | 46 mg | The Coca-Cola Company’s current FAQ figure |
| Diet Pepsi | 12 fl oz | 35 mg | Pepsi’s current U.S. FAQ figure |
Therefore, the direct comparison is:
- Regular: Pepsi is higher by 4 mg per 12 ounces.
- Diet: Diet Coke is higher by 11 mg per 12 ounces.
Four milligrams is a modest difference. Relative to Coke’s 34 mg, Pepsi’s 38 mg is about 12% higher, but both are in the same general caffeine range for colas.
#1 Best Overall
Why regular Pepsi comes out higher
Caffeine concentration is easiest to compare after converting each drink to the same volume. Using the manufacturers’ 12-ounce figures, regular Coke supplies about 2.83 mg per fluid ounce (34 ÷ 12), while regular Pepsi supplies about 3.17 mg per fluid ounce (38 ÷ 12).
That concentration gap explains why Pepsi remains higher when the servings are equal. It does not mean every Pepsi package contains more caffeine than every Coke package: a larger Coke bottle can contain more total caffeine than a smaller Pepsi can simply because it holds more liquid.
What the 4-mg difference feels like in practice
A 12-ounce regular Pepsi gives you only 4 mg more caffeine than a 12-ounce regular Coke. If you are counting total daily caffeine, that difference matters only as part of the day’s total from coffee, tea, energy drinks, chocolate, medicines and other sources. For many people, the choice between the two is more likely to be decided by taste, sugar, price or package size than by a four-milligram spread.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteWhy the diet comparison reverses
Diet Coke and Diet Pepsi do not follow the ranking of their regular counterparts. Diet Coke’s stated 46 mg per 12 ounces is 11 mg above Diet Pepsi’s 35 mg. On a per-ounce basis, that is approximately 3.83 mg for Diet Coke and 2.92 mg for Diet Pepsi.
Sweetener and caffeine are separate formulation choices. A drink with no sugar or fewer calories is not automatically lower in caffeine. “Diet,” “zero sugar,” and “regular” describe different recipe characteristics; you must compare the caffeine declaration for the specific product.
Rank #2
- Ideal for Gifting
- Ideal for a bookworm
- Compact for travelling
Do not assume zero-sugar versions match diet versions
Names such as “diet,” “zero sugar,” “caffeine-free” and regional product names can refer to different formulas. The figures above are for the products explicitly identified in the table. If a can says caffeine-free, its caffeine content should be zero or effectively zero under the applicable labeling rules, but confirm the package rather than inferring from the brand name.
What laboratory testing found
A peer-reviewed study published in the Journal of Analytical Toxicology in 2007 used high-performance liquid chromatography to measure caffeine in 56 national-brand and 75 private-label carbonated beverages. Its results for the four products were close to the companies’ current declarations:
| Product tested | Measured caffeine per 12 oz | Manufacturer figure cited above | Difference |
|---|---|---|---|
| Coca-Cola | 33.9 mg | 34 mg | 0.1 mg lower |
| Pepsi | 38.9 mg | 38 mg | 0.9 mg higher |
| Diet Coke | 46.3 mg | 46 mg | 0.3 mg higher |
| Diet Pepsi | 36.7 mg | 35 mg | 1.7 mg higher |
These are measurements from products analyzed in that 2007 study, not a guarantee that every current can or every country’s formulation will test identically. They do, however, support the same ordering: Pepsi slightly above Coke among the regular versions, and Diet Coke above Diet Pepsi.
How package size changes the total caffeine
The label figures are for 12 ounces. If the same formulation is sold in another size, a proportional estimate can be made with this formula:
estimated caffeine = (caffeine per 12 oz ÷ 12) × package ounces
The following estimates use the stated 12-ounce numbers and assume the recipe is unchanged. They are not substitutes for the package label.
| Product | 12 oz | 16 oz estimate | 20 oz estimate |
|---|---|---|---|
| Coca-Cola (regular) | 34 mg | 45.3 mg | 56.7 mg |
| Pepsi (regular) | 38 mg | 50.7 mg | 63.3 mg |
| Diet Coke | 46 mg | 61.3 mg | 76.7 mg |
| Diet Pepsi | 35 mg | 46.7 mg | 58.3 mg |
For example, choosing a 20-ounce Diet Coke instead of a 12-ounce can could add roughly 31 mg under that proportional assumption. Fountain drinks require extra care because cup sizes, ice and dispensing formulas vary; the volume printed or posted for that serving is the relevant starting point.
Country, formulation and label differences
Caffeine numbers are not universal worldwide. Companies can change recipes, sweeteners and permitted additives by market. Even within one country, regular, diet, zero-sugar and caffeine-free versions may carry different amounts.
Where to verify the number on the package
- 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.
- Use the serving size printed on that package. A “per can” number is meaningful only when the can size is known.
- Check the exact flavor and variant; a cola-flavored product is not necessarily the same formula as the flagship regular or diet drink.
If an online chart conflicts with your can, the package for the product and market you are consuming is the more relevant reference. Reformulations and different container sizes can make an otherwise accurate chart look wrong for your purchase.
How cola caffeine compares with a daily limit
Health Canada’s 2025 guidance gives typical ranges of 36–46 mg for a 12-ounce regular cola and 39–50 mg for a 12-ounce diet cola. Its recommended maximum for adults aged 18 and over is 400 mg of caffeine per day.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Rank #4
Against that 400-mg reference, one 12-ounce serving represents approximately:
| Drink | Caffeine | Share of 400 mg |
|---|---|---|
| Coca-Cola (regular) | 34 mg | 8.5% |
| Pepsi (regular) | 38 mg | 9.5% |
| Diet Coke | 46 mg | 11.5% |
| Diet Pepsi | 35 mg | 8.75% |
The 400-mg figure is a population guideline for adults, not a personal target or a promise that everyone will feel fine at that amount. Sensitivity varies, and your total includes caffeine from every source consumed that day. If caffeine causes insomnia, jitteriness, palpitations, anxiety, stomach upset or headaches, your practical limit may be lower. People with medical conditions, those taking certain medicines and anyone who has been given individualized advice should follow that advice rather than relying on a general number.
How to compare caffeine when shopping
If you are choosing between multipacks or container sizes, compare both caffeine and cost on the same basis. A larger package may have a lower price per ounce but still deliver more caffeine per serving.
- Identify the exact variant. Write down whether it is regular, diet, zero sugar or caffeine-free, plus the flavor.
- Record the labeled serving size. Do not compare a 12-ounce can with a 20-ounce bottle as though they were equal servings.
- Read the caffeine statement. Use the manufacturer’s per-serving number when it is printed; otherwise, contact the manufacturer or use the package’s ingredient and nutrition information.
- Normalize the price. Divide the shelf price by the total fluid ounces or by the number of 12-ounce-equivalent servings, depending on what you are budgeting.
- Normalize the caffeine. Divide total package caffeine by the number of servings so the comparison is not distorted by container size.
- Check the date and market. A chart from another country or an older product page may not describe the can in your cart.
Keep sugar and calorie comparisons separate from caffeine. A lower-sugar choice can still contain more caffeine, as the Diet Coke and Diet Pepsi figures demonstrate.
Which one should you choose?
If you want the lower caffeine regular cola
Choose regular Coke among the two standard 12-ounce products listed here: 34 mg versus Pepsi’s 38 mg. The difference is small, so container size can outweigh the brand difference.
Best Value
- It can be a gift option
- Comes with secure packaging
- Helpful in various ways
If you want the lower caffeine diet cola
Choose Diet Pepsi among the two listed diet products: 35 mg versus Diet Coke’s 46 mg per 12 ounces.
If you want to minimize caffeine regardless of brand
Look specifically for a caffeine-free product and verify the label. Otherwise, choose the smallest serving that satisfies you, count caffeine from all beverages and foods, and avoid assuming that diet or zero sugar means low caffeine.
If you are choosing for sugar or calories
Make that a separate decision. The caffeine ranking does not tell you which drink has more sugar, fewer calories or a particular sweetener. Read the Nutrition Facts panel for those attributes.
Recommended Free Tools
Bottom line for Coke versus Pepsi
At equal 12-ounce servings, regular Pepsi leads regular Coke by 4 mg of caffeine (38 mg versus 34 mg). Diet Coke leads Diet Pepsi by 11 mg (46 mg versus 35 mg). Treat those as product- and market-specific label values, scale them for larger servings only as an estimate, and check the package whenever the formulation or country may differ.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
