How much caffeine is in Coke? (And Diet Coke)

How much caffeine is in a can of Coke and Diet Coke?

A 12 fl oz can of Coca-Cola has 34 mg of caffeine; a can of Diet Coke has 46 mg. Those are Coca-Cola’s own figures, and the US caffeine FAQ, the Diet Coke product page and the label pages all agree on them. Plenty of Coke is not sold in a can, though, and the bottle in your hand has its own number.

Coca-Cola runs a SmartLabel site that prints the label for each US product by barcode, and most of its Coke and Diet Coke pages up to 20 fl oz have a “Caffeine Content” line for the whole can or bottle. We read every Coca-Cola and Diet Coke size on it, then read them again.

Diet means the calories. Somebody at Coca-Cola read it as permission to add caffeine

Read down the columns and the pattern is plain. Each drink holds its strength at every size, so the bottle is just more of the can.

Our arithmetic from Coca-Cola’s US SmartLabel pages: across the cans and bottles up to 20 fl oz, Coca-Cola works out to 2.8 to 2.9 mg of caffeine per fluid ounce and Diet Coke to 3.7 to 3.8 mg. Size for size, Diet Coke states 30% to 36% more caffeine than Coca-Cola. 23534535536537538539540541542543544545553554555556557558559560561562563

Why does Diet Coke have more caffeine than regular Coke?

The size of the gap is easy. The reason is not. By our arithmetic a can of Diet Coke has 12 mg more than a can of Coke, about 35% more, and in a 20 fl oz bottle the gap grows to 19 mg.

Coca-Cola’s US pages print both numbers and say nothing about why. The only explanation from the company we could find is twelve years old, secondhand, and from its British arm about British Diet Coke.

The only reason from Coca-Cola we found for Diet Coke’s extra caffeine is a 2014 trade-press report: BeverageDaily.com (whose archive is now on FoodNavigator.com) printed a statement from an unnamed Coca-Cola spokesperson, given for Coca-Cola Great Britain about UK Diet Coke: “There are slightly different amounts of caffeine in different brands to contribute to their distinct flavour profiles.” Coca-Cola’s US pages give the figures and no reason. 576

Coca-Cola says the extra caffeine in Diet Coke is for flavor. I have never once tasted my heart rate

Whatever the reason, each recipe has its own setting, and the sweetener alone does not decide it. Diet Coke Sweetened with Splenda states 46 mg, the same as Diet Coke. Diet Coke Plant-Based Sweeteners, which the label says is sweetened with monk fruit and stevia extracts, states 50 mg a can and 31 mg in a mini can. It is on SmartLabel but not on Coca-Cola’s Diet Coke products page. Diet Cherry Coke goes the other way, down to 34 mg, level with regular Coke.

How much caffeine is in a 20 oz Coke or a 2-liter?

A 20 fl oz bottle of Coke states 57 mg and a 20 fl oz Diet Coke 76 mg. That bottle of Diet Coke has more than three times the caffeine of a mini can of Coke.

Above 20 fl oz the label changes how it counts. The 24 fl oz, 1-liter, 1.25-liter, 2-liter and 3-liter bottles print caffeine per 12 fl oz serving only: 34 mg for Coke and 46 mg for Diet Coke, the same as the can. The label stops at the serving, so here is the whole bottle, marked as ours.

Our arithmetic, not Coca-Cola’s: the SmartLabel pages for the 2 liter (67.6 fl oz) and 3 liter (101.4 fl oz) bottles state caffeine per 12 fl oz serving only, 34 mg for Coca-Cola and 46 mg for Diet Coke, and print no whole-bottle figure. At that strength a 2 liter bottle holds about 192 mg of caffeine as Coca-Cola and about 259 mg as Diet Coke; a 3 liter bottle about 287 mg and about 389 mg. 549567550568

A big bottle of Diet Coke is a party size. Drink it alone and it is a personality

The same labels settle a question about the other Coke. Coca-Cola Zero Sugar prints 21 mg for the mini can, 48 mg for the 16.9 fl oz bottle and 57 mg for the 20 fl oz, the same as regular Coke at each size. Does Coke Zero have caffeine has the rest of that family.

Do Cherry Coke, Mexican Coke and caffeine-free Coke have caffeine?

• Coca-Cola Cherry: yes, 34 mg a can, the same as Coke. Coca-Cola Vanilla states 34 mg too.
• Coca-Cola Mexico: yes. Its label states 34 mg for the 12 fl oz bottle and 48 mg for 16.9 fl oz, the same as US Coke. The sugar is not always what you paid for: the 12 fl oz label lists cane sugar, the 16.9 fl oz label high fructose corn syrup.
• Diet Cherry Coke: yes, 34 mg a can.
• Caffeine Free Coca-Cola and Caffeine Free Diet Coke: no. Coca-Cola says in words that they have no caffeine, and their label pages print no caffeine figure.

Diet Coke flavors such as Feisty Cherry and Ginger Lime are not on Coca-Cola’s US Diet Coke products page or its label site, and we found no caffeine figure from the company for them. The label site does list a Diet Coke Lime, with caffeine in its ingredients and no figure. If you have an old can, the can is the source. More colas, and the ones with none, are in sodas without caffeine and does Pepsi have caffeine.

Is the caffeine on a Coke label accurate?

Where it has been checked, yes. A 2007 study measured 33.9 mg in Coca-Cola and 46.3 mg in Diet Coke per 12 oz, against labels of 34 mg and 46 mg.

USDA’s food tables come at it from another side. They do not name brands, but they analyzed cola and diet cola samples and the averages land close to the two labels.

USDA’s SR Legacy table, from lab analyses, lists regular cola at 9 mg of caffeine per 100 g (6 samples, 9 to 10 mg) and caffeinated diet cola or pepper-type soda with aspartame at 12 mg per 100 g (7 samples, 3 to 20 mg). Brands are not named. With USDA’s own 12 fl oz weights (370 g and 355 g), that is about 33.3 mg and about 42.6 mg a can: our arithmetic. 577578

Note the spread on the diet side: USDA’s samples run 3–20 mg per 100 g, because that entry lumps caffeinated diet colas and pepper-type sodas sweetened with aspartame together. For Diet Coke itself, the label and the lab agree. The method page explains how we treat a label against a measurement.

How many Diet Cokes a day is too much caffeine?

Our arithmetic against the 400 mg a day that EFSA says raises no safety concern for healthy adults who are not pregnant: about 8.7 cans of Diet Coke (46 mg) or 5.3 bottles of 20 fl oz (76 mg), counting no other caffeine. 12256322

That is a daily total with nothing else in it, and nobody’s day has nothing else in it. A 200 ml filter coffee is about 80 mg, so a can of Diet Coke is a bit over half a cup and a 20 fl oz bottle is close to a whole one. The full list of drinks has the rest, and how much caffeine is in a cup of coffee has the cup.

The total matters less than the timing. Caffeine’s half-life in healthy adults averages 4 hours, so the Diet Coke with dinner is still partly there at midnight. How long caffeine stays in your system has the arithmetic.