If you’re anything like us, your day doesn’t really start until that first sip of coffee hits. Whether it’s a sleepy morning ritual or the much-needed pause between meetings, coffee does more than warm your hands — it sharpens your focus, wakes you up, and gives you a sense of control in an otherwise chaotic world.

And at the heart of that ritual? Caffeine.

But what exactly is caffeine? Why does it work the way it does? How much is safe? And where do different coffees stack up in the caffeine stakes?

We thought it was time we unpacked all this — with a little less science jargon, and a lot more common sense.

So, What Is Caffeine?

Caffeine is a naturally occurring stimulant. It's found in the seeds, leaves, and fruits of various plants — including our beloved coffee beans. In fact, caffeine is part of the plant’s defence mechanism. It helps ward off insects and slows the growth of competing plants nearby by seeping into the soil.

Nature’s way of being quietly competitive.

From a chemistry perspective, caffeine is classified as a methylxanthine — a group of compounds that stimulate the central nervous system. When you drink a coffee, caffeine gets absorbed into your bloodstream and makes its way to your brain. There, it blocks a chemical called adenosine, which is responsible for making you feel drowsy throughout the day. With adenosine held at bay, your brain starts firing on all cylinders.

How Much Caffeine Is in a Cup of Coffee?

Here’s where things get slightly less straightforward — because caffeine levels in coffee aren’t one-size-fits-all. It varies based on bean variety, roast profile, grind size, brew method, serving size, and even the water-to-coffee ratio.

But to give you a rough idea:

• A single espresso shot (about 30ml) typically contains 60–80mg of caffeine
  

• A standard flat white or latte (double espresso + milk) will land between 120–150mg
  

• A filter or drip coffee (around 300ml) can range from 90–140mg
  

• Decaf, despite the name, still contains a tiny amount — usually around 2–5mg per cup
  

Fun fact: light roasts often contain more caffeine than dark roasts by dry weight, because the beans are denser. But dark roasts tend to have more volume per scoop, which can swing the balance back. It’s a subtle but fascinating trade-off.

So if you’re brewing your own, just know that strength isn’t always flavour-based — sometimes, it’s chemical.

How Much Caffeine Should You Have in a Day?

The general consensus from most health authorities (including the NHS and EFSA) is that a healthy adult can safely consume up to 400mg of caffeine per day.

That’s equivalent to about:

• 3 to 4 strong coffees
  

• 5 or so cups of brewed filter
  

• Or a couple of double-shot lattes, depending on your pour

Pregnant individuals are advised to stick closer to 200mg per day, and those sensitive to caffeine (you’ll know who you are — the heart-racers and the ceiling-staring night owls) may want to keep things even lower.

It’s not about rules, though — it’s about rhythm. Some people metabolise caffeine slowly, others seem genetically wired to run on triple espressos and pure optimism. What matters is knowing your personal threshold and using caffeine intentionally, not habitually.

What Happens If You Have Too Much?

A bit of caffeine is a good thing — a nudge, a spark, a mental stretch. But too much? That’s when things get twitchy.

Overdo it and you may experience:

• Restlessness or shaky hands
  

• Anxiety or racing thoughts
  

• Digestive discomfort
  

• Difficulty sleeping (even hours later)
  

• Increased heart rate or palpitations
  

Most of us have been there — the over-caffeinated buzz where your brain feels like it’s running laps around itself. It’s not pleasant. But it’s also not permanent.

Caffeine typically clears from your system within 6 to 8 hours, though the half-life varies depending on age, genetics, and liver function. If you’re struggling to sleep, a good rule of thumb is to cut off caffeine by 2pm, especially if your coffee is on the strong side.

Let’s Talk About Dry Weight vs Brewed Strength

In the coffee world, we sometimes talk about caffeine content in terms of dry weight — that is, how much caffeine is present in the ground, roasted beans before they’re brewed.

For example, Arabica beans (which we use at St Martins) tend to have around 1.2–1.5% caffeine by dry weight. Robusta beans, by contrast, contain nearly double that — up to 2.7%. That’s why some supermarket blends with Robusta can feel a bit punchier, even if they taste flatter.

But caffeine content in your actual cup depends on how much of that dry weight ends up in the final brew. Brewing method matters. A long steep in a French press will extract more caffeine than a quick pour-over. A double shot of espresso pulls a higher concentration into a smaller volume.

So while dry weight gives us a starting point, the real question is: how much do you actually drink, and how often?

The Hidden Benefits of Caffeine

Beyond the pick-me-up, caffeine has some surprising upsides. Studies have linked moderate caffeine intake to:

• Improved alertness, concentration, and reaction time
  

• Boosted memory and learning speed (especially in sleep-deprived individuals)
  

• Enhanced physical performance, particularly endurance
  

• A reduced risk of Parkinson’s disease and Alzheimer’s
  

• Lower chances of developing type 2 diabetes
  

• Even — believe it or not — a longer life expectancy
  

Most of these benefits come from coffee itself, not caffeine alone. The antioxidant compounds in brewed coffee (like chlorogenic acid) work hand-in-hand with caffeine to support brain health and metabolism. So while you might get a caffeine hit from an energy drink, you’re not getting the rest of the package.

Is Caffeine Addictive?

It depends how you define it.

Caffeine is technically a dependency-forming stimulant. Regular drinkers often develop a tolerance, meaning they need more to feel the same effect. And sudden withdrawal — like skipping your morning brew — can trigger headaches, irritability, and fatigue for a few days.

But compared to substances like nicotine or alcohol, caffeine has a much milder dependency profile. It’s not chemically addictive in the same way, and for most people, the “addiction” is more about ritual than requirement.

We say: if it’s bringing you joy, helping you focus, and not messing with your sleep or your gut, keep sipping.

Caffeine in Decaf? Yep — Just a Little

One of the biggest myths we hear is that decaf has zero caffeine. In reality, no decaf is 100% caffeine-free.

Thanks to the way decaffeination works (whether it’s the Swiss Water®, or another method), trace amounts of caffeine remain in the bean. Usually it’s no more than 2 to 5 milligrams per cup — barely enough to register, but technically still present.

It’s about 97–99% less caffeine than the original, which is why our Tasty Decaf still feels like a proper brew without the buzz. Perfect for evenings, late-night creative sessions, or those cutting back without giving up the taste.

Final Thoughts: Use Caffeine With Purpose

At the end of the day, caffeine is a tool. A potent one. When used with purpose — not just out of habit — it can be a game-changer.

It can lift your mornings, spark ideas, anchor conversations, fuel workouts, and smooth over that awkward 3pm lull.

But like any tool, it works best in skilled hands. Knowing how it works — and how it works for you — helps you get the benefits without the downsides.

So whether you're a one-a-day kind of person or someone who operates in a steady buzz from dawn to dusk, remember this:

Good caffeine comes from great coffee.
And great coffee? Well, that’s what we’re here for.

Find your perfect coffee by visiting our store here