Diet Pepsi vs Diet Coke Caffeine: 35 mg vs 46 mg

Diet Coke and Diet Pepsi share several label lines, including 0 g sugar, caramel color, phosphoric acid, citric acid and potassium benzoate. Diet Coke lists 46 mg caffeine per 12 fl oz can, while Diet Pepsi's roughly 35 mg figure is a calculation from a 20 fl oz bottle label, not a printed can value. Diet Coke is sweetened with aspartame only, and the current Diet Pepsi label lists aspartame plus acesulfame potassium.

Key takeaways

• Diet Coke lists 46 mg caffeine per 12 fl oz, a printed figure from Coca-Cola. Diet Pepsi's roughly 35 mg is calculated from a 20 fl oz bottle label.
• Diet Coke is sweetened with aspartame only. The current Diet Pepsi label lists aspartame plus acesulfame potassium, and older USDA data shows a sucralose-based Diet Pepsi formula.
• Sodium is 40 mg per 12 fl oz for Diet Coke and 35 mg per can for Diet Pepsi on Open Food Facts, with an older USDA Diet Pepsi record at 36 mg.
• Both drinks share caramel color, phosphoric acid, citric acid, potassium benzoate and 0 g sugar.

Diet Pepsi vs Diet Coke at a Glance: Which Label Facts Actually Differ?

The table puts the main label fields next to each other. Values are per 12 fl oz can unless noted, and 'Not disclosed' means the value is not in the label data cited in this article.

Label field	Diet Pepsi	Diet Coke
Caffeine per 12 fl oz	About 35 mg (calculated from a 20 fl oz bottle, not printed on the can)	46 mg (printed by Coca-Cola)
Sweeteners (current label)	Aspartame and acesulfame potassium	Aspartame only
Sodium per 12 fl oz	35 mg (Open Food Facts can record)	40 mg (2% DV)
Sugars	0 g	0 g, including 0 g added sugars
Calories	0 (USDA 12 fl oz record)	0 (Coca-Cola US product page, 12 fl oz)
Acids	Phosphoric acid, citric acid	Phosphoric acid, citric acid
Preservative	Potassium benzoate	Potassium benzoate
Color	Caramel color	Caramel color
Phenylalanine line	Not disclosed in cited sources	Yes: PHENYLKETONURICS: CONTAINS PHENYLALANINE

Diet Pepsi figures come from Open Food Facts label records and a USDA FoodData Central record. Diet Coke figures come from Coca-Cola's US product page.

The differences that show up most clearly are the caffeine figure, the sweetener list and the sodium figure. The acids, preservative, color and sugar lines match closely.

Diet Pepsi vs Diet Coke: How Much Caffeine Is in a 12 oz Can?

How much caffeine is in Diet Pepsi 12 oz?

No printed caffeine value for a 12 fl oz Diet Pepsi can was available. The roughly 35 mg figure is a calculation: the 20 fl oz (591 ml) bottle on Open Food Facts lists 59 mg, and 59 mg x 12/20 is about 35 mg per 12 fl oz.

Scaling assumes the bottle and the can carry the same caffeine level, and the label data cited here does not confirm that. Treat 35 mg as an estimate, not a label value.

Does Diet Coke have 46 mg of caffeine per 12 oz?

Yes. Coca-Cola's US Diet Coke product page and its caffeine FAQ both list 46 mg caffeine per 12 fl oz can of Diet Coke. The same FAQ gives 34 mg for a 12 oz can of Coke and places a 12 oz coffee at 140 mg or more.

Coca-Cola also lists Caffeine Free Diet Coke, which has the same ingredients minus caffeine. For context, FDA's caffeine consumer update cites 400 mg a day as an amount not generally associated with negative effects for most adults. The same update lists 12 oz caffeinated soft drinks at 23 to 83 mg. Caffeine sensitivity varies, so the same number may matter more to some readers than to others.

For a Coca-Cola comparison focused on the same caffeine question, see Diet Coke vs Coke Caffeine: 46 mg vs 34 mg per 12 oz Can.

Diet Pepsi vs Diet Coke: Aspartame Alone or Aspartame Plus Ace-K?

Does Diet Coke have aspartame?

Yes. Aspartame is the only sweetener in the Diet Coke ingredient statement, which lists it alongside carbonated water, caramel color, phosphoric acid and the other ingredients.

Does Diet Pepsi have aspartame?

Yes. The current Diet Pepsi ingredient text on Open Food Facts, from a 12 fl oz can record with a 2020 ingredient photo and a 20 fl oz bottle record with a 2022 photo, lists aspartame.

Does Diet Pepsi have sucralose?

Not on those current label photos. A USDA FoodData Central branded record for a Diet Pepsi Cola 12 fl oz aluminum can, with label data dated 2018, lists sucralose alongside acesulfame potassium. That USDA record lists sucralose for an older formula. The date PepsiCo switched back to aspartame is not disclosed in the label data cited here.

Acesulfame potassium, often called ace-K, appears near the end of the Diet Pepsi ingredient statement. FDA says it is about 200 times sweeter than sugar, was approved for specific food categories in 1988, and was approved as a general-purpose sweetener in 2003. The amount of aspartame or acesulfame potassium per can is not disclosed for either drink.

In plain terms, Diet Coke's sweetener line names one ingredient, while Diet Pepsi's current line names two. Both labels show 0 g sugar. For a Pepsi-side comparison, see Pepsi Zero Sugar vs Diet Pepsi: Ingredients and Caffeine.

Diet Pepsi vs Diet Coke: How Much Sodium Is in Each 12 oz Can?

Diet Coke lists 40 mg sodium per 12 fl oz, which Coca-Cola shows as 2% DV. Diet Pepsi's 12 fl oz can on Open Food Facts lists 35 mg per can.

A USDA FoodData Central record for Diet Pepsi Cola 12 fl oz aluminum can lists 36 mg sodium per 12 fl oz, within 1 mg of the Open Food Facts figure. That match applies to label data only, not to the drink as it is sold today. The USDA record is based on 2018 label data, so it may reflect an older formulation. The 20 fl oz Diet Pepsi bottle on Open Food Facts lists 60 mg sodium, but that is a different package size and is not directly comparable to a 12 fl oz can.

Check the Nutrition Facts panel on your can, because packaging can change from year to year. Whether Coca-Cola's page uses the same 12 oz label as every US bottler is not disclosed.

Diet Pepsi vs Diet Coke: Which Acids and Preservatives Appear on the Label?

Both labels list phosphoric acid and citric acid. Both also list potassium benzoate and caramel color. Diet Coke's label says potassium benzoate is there to protect taste, while Diet Pepsi's says it preserves freshness.

The label data cited here names these acids but does not describe their levels beyond the ingredient names. The amount of potassium benzoate per can is not disclosed for either drink.

Caramel color is a color additive. FDA says caramel color is exempt from batch certification but still requires FDA approval. Neither label's caramel color class is disclosed, so the specific type used by either brand is unknown.

Diet Pepsi vs Diet Coke: What Is the Full Ingredient List Side by Side?

The ingredient statements below appear as printed in the cited label data, in label order.

Diet Coke (Coca-Cola US product page, 12 fl oz can): CARBONATED WATER, CARAMEL COLOR, ASPARTAME, PHOSPHORIC ACID, POTASSIUM BENZOATE (TO PROTECT TASTE), NATURAL FLAVORS, CITRIC ACID, CAFFEINE. PHENYLKETONURICS: CONTAINS PHENYLALANINE

Diet Pepsi (Open Food Facts, 12 fl oz can): CARBONATED WATER, CARAMEL COLOR, ASPARTAME, PHOSPHORIC ACID, POTASSIUM BENZOATE (PRESERVES FRESHNESS), CAFFEINE, CITRIC ACID, NATURAL FLAVOR, ACESULFAME POTASSIUM.

Older Diet Pepsi formula (USDA FoodData Central, 2018 label data): CARBONATED WATER, CARAMEL COLOR, PHOSPHORIC ACID, POTASSIUM BENZOATE (PRESERVES FRESHNESS), SUCRALOSE, ACESULFAME POTASSIUM, CAFFEINE, NATURAL FLAVOR, CITRIC ACID.

Two wording differences stand out. Diet Coke lists NATURAL FLAVORS in the plural, while Diet Pepsi lists NATURAL FLAVOR in the singular, and the order of several ingredients differs. What the natural flavors are in either drink is not disclosed, so the wording difference should not be read as a difference in content.

Did Recent Regulatory Reviews Change Aspartame or Ace-K in Diet Pepsi or Diet Coke?

None of the reviews below has changed the formula of either drink. The findings describe evidence and acceptable intake levels, not the contents of a specific can.

FDA says aspartame is about 200 times sweeter than sugar and that the established acceptable daily intake (ADI) 'continues to be protective of public health.' FDA disagrees with the July 14, 2023 International Agency for Research on Cancer (IARC) classification of aspartame as 'possibly carcinogenic to humans' (Group 2B), and notes that the Joint FAO/WHO Expert Committee on Food Additives (JECFA) did not change the ADI.

IARC classifications assess the strength of evidence for a hazard, not the amount in a single can. Diet Coke, which is sweetened with aspartame only, and Diet Pepsi, which combines aspartame and acesulfame potassium, are not described as changed by these reviews.

Diet Pepsi vs Diet Coke: Phenylalanine Labels and Sensitive Groups

FDA says people with phenylketonuria (PKU) should avoid or restrict aspartame, and that labels must carry a phenylalanine statement. The Diet Coke label carries that statement: PHENYLKETONURICS: CONTAINS PHENYLALANINE.

The Open Food Facts ingredient text for Diet Pepsi cited here does not include a phenylalanine line. Whether the physical can carries one is not disclosed in the label data cited here, so check the can itself. Questions about PKU and diet are best taken to a healthcare professional.

Caffeine is the other factor for some readers. FDA's 400 mg a day figure applies to most adults and does not address every group. Questions about pregnancy, medications or caffeine sensitivity are individual, and these label facts cannot answer them. This article is educational only and does not recommend what anyone should drink.

How Do You Check Caffeine, Sweeteners and Sodium on Your Own Diet Soda Label?

Use this checklist on any diet cola, including the two above:

• Confirm the serving size. Figures in this article are per 12 fl oz unless noted, while the Diet Pepsi bottle figures are per 20 fl oz.
• Caffeine appears in the ingredient list, but a milligram value may not be printed on the can. Check the brand page or packaging for a printed mg figure.
• Scan the sweetener names: aspartame, acesulfame potassium and sucralose are each named separately in ingredient text.
• Read sodium as milligrams per serving and the % Daily Value on the Nutrition Facts panel.
• Look for a phenylalanine statement if PKU is relevant to you.
• Note flavor wording. Natural flavor and natural flavors are both listed, and their contents are not disclosed.
• Recheck when a product changes. The USDA record lists sucralose for an older Diet Pepsi formula, so an older photo or database entry may not match the can on the shelf.

Where Can You Read More: Related Diet Soda Comparisons on Aurascan?

These guides compare neighboring labels in the same side-by-side format:

• Coke Zero vs Diet Coke: Ingredients, Taste and Caffeine (34 vs 46 mg)
• The 5 Sodas People Scan Most: Sweeteners, Acids and Colors

Scan the next diet soda you pick up with the Aurascan app and read its label facts for yourself.