Last Updated: 10. February 2020

How Much Caffeine Is in a Cup of Coffee? [Caffeine Guide]

By Helen Cartwright

Realistically, there is one main reason why we drink coffee: for the caffeine.

There’s nothing like the enticing smell of fresh coffee in the morning, and we coffee enthusiasts can’t get enough of the bold, rich taste.

However, caffeine is what helps us wake up. For this reason, you can overserve coffee. This is why it’s crucial to understand how much caffeine we’re consuming when we drink coffee.

In this article, we’ll answer the question, “How much caffeine is in a cup of coffee?” We’ll also go over the science behind caffeine, including its benefits and side effects.

In-Short

Caffeine is a stimulant which affects the central nervous system, providing a boost in alertness.
On average, a 240 ml cup of coffee contains 96 mg of caffeine, or 0.4 mg per ml.
The amount of caffeine in coffee can vary depending on the variant. Espresso, for example, contains 64 mg of caffeine per 30 ml serving. That’s 2.1 mg of caffeine per ml!
Having too much caffeine can potentially result in serious side effects including headaches, jitteriness, nausea, and high blood pressure.
Caffeine also provides health benefits such as improved alertness and better cognitive performance.
To enjoy the benefits of caffeine while minimising the side effects, adults should limit themselves to 400 mg of caffeine per day, which is approximately 4 cups of coffee.

What Is Caffeine, Anyway?

Caffeine is a drug naturally found in coffee, as well as tea, coffee, and other items such as chocolate. It acts as a stimulant, giving a boost to the central nervous system and increasing alertness.

This is why caffeine is commonly used to stay awake and energetic. It is also used as a key ingredient in medications which treat migraines and drowsiness.

Unlike other drugs, caffeine is legal and widely accepted in society. Some may even overlook its status as a drug because of its prevalence in society.

More than 50% of Americans 18 or older drink coffee daily. To put things in a better perspective, about 90% of Americans regularly consume caffeine in some form.

How Much Caffeine Is In a Cup of Coffee?

The average amount of caffeine in a 240 ml serving of coffee is 96 mg. With 400 mg of caffeine being the average daily limit for consumption, that means you could drink approximately 4 cups of coffee a day.

In contrast, decaf coffee averages at 2 mg of caffeine per 240 ml serving. This shows that although decaf isn’t completely free of caffeine, the amount of caffeine is insignificant.

But be careful, as there can be a huge difference in the amount of caffeine between coffee types and brewing methods.

We have a page that goes into more detail about the amount of caffeine in different coffee drinks. For now, let’s go over the most common variants of coffee.

Caffeine Content in Coffee Variants

These are the most popular types of coffee preparation with their averaged caffeine content.

Beverage	Serving Size	Caffeine Content	Caffeine/ml
Brewed coffee	240 ml	96 mg	0.4 mg
Brewed coffee, decaf	240 ml	2 mg	0.01 mg
Espresso	30 ml	64 mg	2.1 mg
Cold brew	240 ml	100 mg	0.4 mg
Instant (yuck!)	240 ml	120 mg	0.5 mg

How Does It Compare with Other Beverages?

As you’ll notice, all but one of the non-coffee beverages below averages at less caffeine per serving than coffee.

Beverage	Serving Size	Caffeine Content	Caffeine/ml
Black tea	240 ml	47 mg	0.2 mg
Green tea	240 ml	28 mg	0.1 mg
Energy drink	240 ml	30 mg	0.1 mg
Energy shot	30 ml	215 mg	7.2 mg
Cola	240 ml	22 mg	0.1 mg

What Affects Caffeine Content?

Several factors affect the amount of caffeine in your coffee.

Coffee variety

There are different types of beans from different plants. Two of the most popular variants are arabica and robusta. Robusta tends to have twice as much caffeine (70 to 80 g per kg of dry coffee) as arabica (35 to 40 g per kg of dry coffee).

Roast type

More of the bean’s natural caffeine levels are retained in light roast coffees, as is the original flavour. The darker the roast, the more caffeine gets lost.
As an example, check out our review of Starbucks Blonde Roast Coffee. We mention that the level of acidity is higher in light roasts than dark roast. This helps show that coffee roasted for shorter periods maintains more of its original properties, such as acidity and caffeine.

Coffee to water ratio

With more coffee to extract from, you get more caffeine. You might want to read up on our article about the best coffee to water ratio for more details on this. For a quick and easy way to calculate the proper coffee to water ratio, use our calculator!

Serving size

If you drink more coffee, that means you ingest more caffeine, right?

The Risks of Too Much Caffeine

Of course, you can have too much of a good thing, and this principle applies to caffeine. Remember, it’s a drug! Here are some things to keep in mind.

How Much Caffeine Should I Have Per Day?

According to the Dietary Guidelines for Americans 2015-2020, adults should limit themselves to 400 mg of caffeine each day. This amount can vary depending on sensitivity to caffeine, and the ability for the body to metabolise it.

The FDA discourages children and adolescents from caffeine consumption. With less body weight in young children and teens, there is less room for caffeine tolerance.

More importantly, caffeine primarily affects the central nervous system. With children’s brains still in development, caffeine can potentially alter this development. Whether or not kids can have coffee is a topic for a whole other article, and luckily, we have one!

What Are the Side Effects of Too Much Caffeine?

The most common side effects of ingesting too much caffeine are:

Headaches
Jittery feeling
Anxiety
Irritability
Increased heart rate and blood pressure
Insomnia
Upset stomach
Nausea
Frequent urination
Nervousness

The Health Benefits of Caffeine

While you should be cautious about the amount of caffeine you consume, it’s important to remember that caffeine can also be good for you.

When used in moderation, caffeine can provide the following health benefits:

Improved memory
Improved alertness
Decreased fatigue
Better cognitive performance

Researchers at the Linus Pauling Institute at Oregon State University in Corvalis suggest that caffeine can help prevent type 2 diabetes, Parkinson’s disease, and liver disease. It also doesn’t appear to significantly increase the risk of heart disease or cancer.

Be mindful of your caffeine intake and limit yourself to about 4 cups of coffee per day. That way, you can enjoy these benefits while lessening (if not eliminating) the negative side effects.