How much caffeine is in a cup of coffee?

The honest answer is that it depends, but that is a useless thing to tell someone who just wants a number. So here are the numbers, and then the reasons they move.

A standard mug of filter coffee — 240ml — carries roughly 95mg of caffeine. That is the figure to hold in your head. Everything else on this page is a variation on it.

Caffeine by brew method

These are typical figures for a normal serving. Real cups vary by roughly 30% either side depending on how you brew, which is exactly what the rest of this article is about.

Brew	Serving	Caffeine
Filter / pour-over	240ml mug	~95mg
Cafetière	240ml mug	80–100mg
Single espresso	30ml	~63mg
Double espresso	60ml	~125mg
Flat white or latte (double)	240ml	~125mg
Instant	1 heaped tsp	60–80mg
Decaf	any method	2–5mg
Black tea (for comparison)	240ml mug	~47mg

In grams, since people do search for it that way: a standard mug of filter coffee holds about 0.095g of caffeine. Caffeine is measured in milligrams for the same reason paracetamol is — the doses are small enough that grams give you an awkward string of zeros.

The one that surprises people is espresso. A single shot has less caffeine than a mug of filter, not more. It is far more concentrated — about 210mg per 100ml against filter’s 40mg per 100ml — but you are drinking 30ml of it rather than 240ml. Concentration and dose are not the same thing, and the espresso reputation comes from the former.

The other one worth flagging is decaf. It is not caffeine-free and it is not allowed to claim it is. UK and EU rules require at least 97% of the caffeine to be removed, which leaves a few milligrams in the cup. Fine for almost everyone, but if you are counting precisely, count it.

The dark roast myth

This is the belief that will not die: darker roast, stronger coffee, more caffeine.

It is wrong, and it is wrong in an interesting way.

Caffeine is remarkably stable under heat. Roasting for longer destroys only a very small amount of it. What roasting definitely does is drive off moisture and expand the bean, so a dark roasted bean is physically larger and lighter than a light roasted one from the same batch.

That is where the confusion comes in, and the answer depends entirely on how you measure:

• By weight — 18g of light roast and 18g of dark roast have almost identical caffeine. Any difference is too small to notice.
• By scoop — a scoop of dark roast beans weighs less than the same scoop of light roast, because the beans are bigger and less dense. So you are using less coffee, and getting slightly less caffeine.

So if you have been reaching for a dark roast for the kick, and you measure with a spoon, you have been very slightly short-changing yourself the whole time. What you were actually tasting was roast character — the smoke, the bitterness, the heaviness — and reading it as strength.

Which is the real point. Strength is a flavour impression. Caffeine is a dose. They are not the same thing and they are not even reliably related.

If you want to know what a roast level actually changes, we wrote about that in roast levels explained.

What genuinely changes the caffeine in your cup

In rough order of how much they matter:

The dose. More coffee, more caffeine. This dwarfs everything else on the list. Going from 15g to 20g in the same brew is a 33% increase, and no amount of fiddling with anything else comes close to that. Weigh it — a set of scales will tell you more about your coffee than any other change you make.

The species. Arabica against robusta is roughly a doubling — robusta carries about 2.2% caffeine by weight against arabica’s 1.2%. Most cheap supermarket blends and most instant coffee lean on robusta, which is part of why a mug of instant can hold its own against a carefully brewed filter.

Contact time. The longer water sits on grounds, the more caffeine comes out. A four-minute cafetière extracts more than a two-and-a-half-minute pour-over at the same dose. Cold brew steeps for sixteen hours, which is why the concentrate is so potent — though by the time you have diluted it in a glass, as in this recipe, you are back in normal territory.

Grind size. Finer grounds have more surface area, so they give up caffeine faster. This is really a lever on contact time by another route. Our grind size guide covers where to set it per method.

Water temperature. Hotter water extracts faster. The effect is real but modest compared to the dose.

Notice what is not on that list: roast level. It is the variable people obsess over and very nearly the only one that does not matter here.

How much is too much

The NHS advises that up to 400mg of caffeine a day is fine for most healthy adults. That is roughly four mugs of filter coffee, or three doubles.

If you are pregnant, the guidance is 200mg a day — about two mugs of filter, and worth remembering that tea, cola and chocolate all count towards it.

Those are general figures from a public health body, not personal advice. People metabolise caffeine at genuinely different rates — some of it genetic — which is why one person sleeps fine after an evening espresso and another is staring at the ceiling at 2am. If caffeine affects you badly, or you are on medication, that is a conversation for your GP or pharmacist rather than a coffee company’s blog.

The practical version

If you want more caffeine: use more coffee, and weigh it.

If you want less: use less coffee, or drink a smaller cup, or go decaf. Switching to a lighter roast will not do it, and switching to a darker one will not get you more.

And if what you actually want is a cup that tastes stronger rather than one that hits harder — heavier, darker, more of a punch in the mouth — that is a different problem with a much better solution. Whiskey Creek and Midnight Ride are the two we roast for exactly that, and a pinch of salt in the grounds will take the harsh edge off a dark roast without touching the strength.