How Much Caffeine Is in a Can of Diet Pepsi? | Exactly 35 mg

You grab a can of Diet Pepsi from the fridge, maybe out of habit or because it fits your diet. If you are also watching your caffeine intake, you might wonder exactly what landed in your glass. The number is smaller than many people assume.

A 12-ounce can of Diet Pepsi contains 35 mg of caffeine. That puts it on the lower end of the soda spectrum, well below a standard cup of coffee and even slightly under regular Pepsi and Diet Coke. Here is a breakdown of where that number comes from and how it stacks up against other drinks.

Official Caffeine Count for Diet Pepsi

PepsiCo’s official product facts page lists exactly 35 mg of caffeine for a 12-ounce can of Diet Pepsi. This is the figure to rely on if you are comparing beverages or logging daily intake.

A 20-ounce bottle of Diet Pepsi contains 59 mg of caffeine. By volume, you get about 2.9 mg of caffeine per fluid ounce. That consistency makes it easy to estimate across different serving sizes.

This places Diet Pepsi in the lower tier of caffeinated sodas, alongside Coke Zero. For someone who wants a cola taste without a strong stimulant effect, it is a common choice.

Why The 35 mg Figure Surprises Soda Drinkers

Many people assume diet colas pack more caffeine to make up for flavor differences. The reality is that Diet Pepsi is one of the milder options on the shelf.

• Diet Pepsi vs. Regular Pepsi: Diet has 35 mg while regular Pepsi has 38 mg. That is only a 3 mg difference between them.
• Diet Pepsi vs. Diet Coke: Diet Coke contains 46 mg per 12-ounce can, which is about 30% more caffeine than Diet Pepsi.
• Diet Pepsi vs. Mountain Dew: Mountain Dew packs 55 mg of caffeine per can, making it one of the strongest mainstream sodas.
• Diet Pepsi vs. Pepsi Max: Pepsi Max is the high-caffeine sibling at 69 mg per can, nearly double the amount in Diet Pepsi.
• Diet Pepsi vs. Coca-Cola Zero: Both sit at 35 mg of caffeine, making them identical in this category.

The variation matters if you drink multiple sodas during the day. Switching from Diet Coke to Diet Pepsi could drop your daily caffeine intake by roughly 33 mg per two cans.

How Diet Pepsi Compares to Coffee and Tea

The most common question is how soda compares to a standard cup of coffee. An 8-ounce serving of brewed coffee contains roughly 95 mg of caffeine, which is nearly three times the amount in a 12-ounce can of Diet Pepsi.

Harvard’s nutrition source notes that the average dark cola contains about 40 mg of caffeine per can, though individual brands vary widely. The Harvard cola caffeine average is a useful benchmark, but Diet Pepsi sits below that average at 35 mg.

Black tea falls somewhere in between with roughly 47 mg per 8-ounce cup. Green tea is lower, averaging around 35 mg per cup. For someone monitoring their total, Diet Pepsi lands closer to green tea than to coffee or black tea.

Drink	Serving Size	Caffeine (mg)
Diet Pepsi	12 oz	35
Regular Pepsi	12 oz	38
Diet Coke	12 oz	46
Mountain Dew	12 oz	55
Brewed Coffee	8 oz	95

As the table shows, Diet Pepsi sits comfortably on the lower rung of the caffeine ladder. When people search for caffeine diet pepsi, the answer typically comes with a comparison to coffee.

How To Confirm The Caffeine Content Yourself

Food labels in the United States are not required to list caffeine amounts unless it is added as a separate ingredient. For Diet Pepsi, caffeine is added, but the exact milligrams rarely appear on the can itself.

1. Check the brand website: PepsiCo publishes a product facts page with caffeine data for every beverage they make.
2. Read the ingredients list: If caffeine is added it will appear in the ingredients, which confirms its presence if not the exact amount.
3. Watch the serving size: A 12-ounce can is 35 mg, but a large fountain cup could be three times that size and contain roughly 93 mg if proportional.
4. Factor in your daily limit: The FDA suggests 400 mg per day for healthy adults is generally safe. One can of Diet Pepsi uses less than 10% of that guideline.

Having the exact number for one serving makes it easier to track your total daily intake without guesswork.

Where Caffeine Comes From In Diet Pepsi

Caffeine is a bitter substance found naturally in coffee, tea, and cacao plants. In most sodas, including Diet Pepsi, it is added during manufacturing to provide a mild stimulant effect and balance out the sweetness of the syrup.

UC Davis explains this in their consumer fact sheet, noting that added caffeine is common in colas. You can read their full breakdown in the much caffeine resource, which covers how different beverages compare.

Some brands offer caffeine-free versions of their sodas, including Diet Pepsi Caffeine Free, for people who want the flavor without any stimulant. Checking the label tells you which version you are buying.

Beverage	Caffeine Source
Diet Pepsi	Added during manufacturing
Brewed Coffee	Naturally occurring
Black Tea	Naturally occurring

The Bottom Line

A 12-ounce can of Diet Pepsi provides 35 mg of caffeine, placing it on the low end of the soda scale. If you are choosing between popular colas, this is one of the lighter options. Checking official brand data remains the most reliable way to know what you are actually drinking.

Your personal tolerance depends heavily on your overall health and any medications, so your doctor or pharmacist can help clarify what fits your individual limits without guessing.