Does Coffee Improve Exam Performance? – What the Science Says

In this article, we will be discussing if coffee is going to help you perform better in your exams and what the downsides of drinking it are.

Quick Answer

Coffee most likely does boost exam performance and you should have it before most exams. However, there are no scientific studies which directly look at exam scores and caffeine intake.

Should You Have Coffee Before Exams?

You should have coffee before most of your exams as it is linked to better cognition and enhanced alertness.

This 1993 study tested over 9000 people. They completed tests of simple reaction time, choice reaction time, incidental verbal memory, and visuospatial reasoning. Improved performance with higher levels of coffee consumption was observed for all tests.

This study shows something that science has shown for a long time; coffee unquestionably improves the performance of simple tasks like reaction time. However, more complex tasks like answering questions in an exam remain uncertain.

Nonetheless, this 2016 review paper stated that up to 300mg of caffeine can enhance performance while minimising side effects like a decrease in alertness and attention. This means that although there are no scientific studies about coffee consumption before exams, there is almost certainly no negative cognitive effects associated with it.

The same paper also discussed how caffeine is great for when you are bored.

If you know that you’re going to struggle to get through your homework or your exam paper because it’s just incredibly dull, having some coffee will get your mind focused like nothing else.

What does this all mean?

It means that you should have coffee before your exams as there is likely to be an increase of attention and alertness while having little side effects for your brain.

But is there any evidence in regards to coffee use and grades over the long term?

white ceramic mug and saucer with coffee beans on brown textile

Does Coffee Give You Better Grades?

So it’s all well and good saying that coffee increases brainpower and helps you concentrate, but does it actually give you better grades?

Unfortunately, no evidence strictly looks at caffeine intake and grades. However, given everything that is known about caffeine, it is safe to say that it does have the potential to make you perform better when studying which results in better performance in exams.

As this 2016 study points out, the benefits of caffeine seem to be highest when a student would be performing in sub-optimal conditions.

What this means is that if you feel groggy and sleep-deprived when studying for your exams, having a bit of coffee will help alleviate the tiredness and make you feel more awake.

If you are already at your peak mental performance, then having coffee is not going to have as big of an effect, but it is still worth taking.

I know that this is not the answer you were looking for. You wanted me to say “yes, having coffee before your exams will increase your exam grades by 50%”.

Unfortunately, that is not how science works.

However, there does seem to be a consensus that caffeine can help with long term memory. Therefore, it can be theorized that caffeine is an excellent resource that should be used periodically throughout your revision and study sessions as you will be able to study for longer and also retain more of the things you learned.

When Is the Best Time to Have Coffee Before an Exam?

So now we know that you should probably be having coffee before your exams, when exactly is the best time to have your coffee?

Right before the exam or a few hours before?

Well, the peak concentration of caffeine in the bloodstream is reached about 0.5 to 3 hours after having the coffee. This may seem like a broad range and that’s because it depends greatly on the person who is taking it.

Everyone is different. However, you can probably assume that you reach a peak concentration of caffeine in about 0.5 to 1 hour.

shallow focus photography of coffee late in mug on table

To make things even more complicated, just because you reached peak concentration doesn’t mean you reach peak performance.

Reaching peak performance may take slightly longer and therefore an exact time of when you should be taking your coffee is hard to give.

The best piece of advice I can give is to try out having coffee in the weeks leading up to your exam and figure out how long it takes for you to feel the effects of the coffee kick in. Try half an hour, one hour and two hours before and see which works best for you.

What Is the Best Type of Coffee to Have?

Is it better to have a mocha, cappuccino or latte? Does it even make a difference?

Well, it doesn’t matter.

The coffee is not what makes your brain get enhanced, it is the caffeine. Therefore, rather than the type of coffee that you are having, it is more important that you look at the milligrams (mg) of caffeine that is present in it.

It’s difficult to give exact numbers but I made this image to should how the mg of caffeine varies in different drinks.

Amount of caffeine in your coffee

Another estimate that can be used is that 8 ounces (237ml) of weak coffee has around 100 mg of caffeine in it, while a strong cup has 175 mg.

But what does mg actually mean?

Mg is just a measure of how much caffeine is in the coffee. It is literally the weight of the caffeine.

If you have never had coffee before and suddenly had 100 mg of caffeine, you would certainly feel the effects of it. However, if you are a regular consumer of coffee you wouldn’t feel much at all.

So when looking at the different levels of caffeine in your coffee, it’s not just that more is better. You have to look at your normal consumption is and figure out what is best for you.

Coffee TypeCaffeine content (mg/100 mL)Serving size (mL)Caffeine content (mg/serving)Caffeine content (high/medium/low)
 Drip method60–10015090–150High
The amount of caffeine in coffee (reference)

Is Tea as Good as Coffee?

Although tea does have some caffeine in it, it does not tend to have as much as coffee.

Therefore, unless you are going to be drinking 5 cups of tea a day, you should probably just stick to coffee before your exams.

Interestingly, if you want your tea to have more caffeine in it, all you have to do is let it brew for longer.

Check out the table below to see how an extra 4 mins of brewing can more than double the caffeine content.

Tea TypeCaffeine content (mg/100 mL)Serving size (mL)Caffeine content (mg/serving)Caffeine content (high/medium/low)
 1-min brew6–221509–33Low
 5-min brew13–3315020–50Low-Medium
Iced Tea6–1035022–36Low-Medium
The amount of caffeine in tea (reference)

What About Energy Drinks?

Energy drinks are a controversial topic, however, they do theoretically help with exam performance.

That’s because they have a solid amount of caffeine in them which means they have the same effect that coffee would have.

However, as you can see from the table below, the caffeine content is still lower than your standard coffee.

Energy Drink TypeCaffeine content (mg/100 mL)Serving size (mL)Caffeine content (mg/serving)Caffeine content (high/medium/low)
 Red Bull®3423580Medium
The amount of caffeine in energy drinks (reference)

How Much Is Too Much?

How much coffee should you have? Is there such a thing as having too much coffee?

Well yes, there is.

You should not be having more than 400 mg of caffeine in a day. That’s the equivalent of 4 cups of brewed coffee.

Most people won’t need to worry about reaching the limit to their coffee consumption, however, it is certainly something that you should be considering if you are going to be having lots of tea and coffee throughout your exam period.

You should take extra care on the day of your exam.

That’s because having more than one or two coffees before your exam will start to give you some of the side-effects of coffee which can be particularly annoying during your exam (see below for more detail).

Even if you are used to having coffee every day, I would suggest that the day before your exam you try and not have your daily cup and instead have some tea. It might be difficult and make you fatigued for the day, however, it will enhance your performance on the day of the exam.

That’s because caffeine works best on an intermittent on-off basis. Having it every day will negate the positive effects on your exam day.

How Long Do the Effects Last?

The caffeine in the coffee has a half-life of 3 to 5 hours. It is important to know the half-life as it gives an idea of how long the coffee will affect you.

The stimulatory effects of caffeine can start as early as 15 minutes after consumption and last as long as 6 hours. Although there will almost certainly be caffeine in your system even 12 hours after consumption, it will be low enough that it shouldn’t affect your sleep.

To ensure your sleep is not interrupted, try not to drink any coffee after 2 pm.

Note that it is also important to adjust when you have coffee based on the strength of the coffee, how long the exam is and the number of exams you may be taking in the day.

Why Coffee Might Not Be Such a Good Idea

Unfortunately, like with all things in life, coffee has its downsides. You will have to balance these with the benefits of having coffee and decide for yourself if it’s the right thing to have before your exam.


If you have it too late at night it almost guaranteed to affect your sleep.

This is especially important as a lot of students use coffee in the days leading up to the exam to help them study for longer and concentrate on the material. Not only does this make coffee less effective on the actual day of the exam (as you will have built up a level of tolerance), it could mean that the sleep leading up to your exam is affected. So be sure to not have any late-night caffeine, even if you are tempted.

Sleep is also an issue if you have multiple exams stretched over many days.

The way to overcome this is to only have coffee on the days of your exams 1 hour before your exam, up to a limit of 2 pm. If your exam is any later than 4 pm you will just have to deal with not having coffee right before.

This will ensure your nighttime sleep is not affected while still having all the benefits listed above.

If you have problems sleeping at night, then ensure you don’t have coffee or tea up to 12 hours before bed. Although the normal recommendation is not to drink it 6-8 hours before bed, it is better to be safe than sorry.

high angle photo of two green mugs filled with coffee


Another side effect of having a lot of coffee is the need to go to the toilet.

Not only is it an inconvenience if you are bursting to go to the bathroom a couple of hours into your exam, but it can also seriously distract you from the questions.

This is more important for people who prefer not to go to the bathroom during an exam to save as much time as possible.

Therefore, I suggest that if you have a problem with using the bathroom, either use a weaker strength of coffee or just avoid it entirely.

Heart Rate and Breathing

If you have too much it could cause your heart rate and breathing rate to pick up significantly. Although this is not dangerous, it can be distracting and cause you to get even more nervous than you already are.

If you have a heart condition then please ensure to see a doctor before consuming high levels of caffeine.

My Experience With Coffee Before Exams

Since learning about the benefits of coffee in my second and third year of medical school, I have consistently used coffee before every one of the exams.

I ensure that the days leading up to the exam I don’t have any coffee to ensure maximum effect on the day itself.

Them I buy myself a mocha from my local supermarket and drink it about 1 hour before the start of my exam.

Unfortunately, I do get slightly jittery and nervous before the exam, which is a side effect of the coffee. It is something I am willing to put up with as it tends to wear off soon after the exam has started and the benefits that the coffee gives me in terms of concentration is well worth the slight jitteriness.

I would therefore recommend it to anyone who is considering trying it out as you may just get an extra few questions right that you wouldn’t have before.


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