If you’ve ever wondered how much caffeine is in a cup of coffee while reaching for a second refill, here’s the short answer: a regular 8-ounce cup of brewed coffee has about 95 milligrams. But that number bounces around more than most people think, depending on what you’re drinking and how it was made.

The quick answer

For plain drip or brewed coffee, plan on roughly 95 mg of caffeine per 8-ounce cup. In practice, most cups land somewhere between 70 and 140 mg. The beans, the grind, the brew time, and — biggest of all — the size of your mug all push that number up or down. A coffee-shop “cup” is usually 12 or 16 ounces, so if you’re drinking a large, you’re getting closer to 200 mg without realizing it.

How caffeine compares by coffee type

Not all coffee is created equal. Here’s what a typical serving of each actually contains:

  • Brewed/drip coffee (8 oz): about 95 mg (range 70–140 mg)
  • Espresso (1 oz shot): about 63 mg
  • Instant coffee (8 oz): about 62 mg
  • Cold brew (12 oz): 150–200 mg — it’s concentrated, so it packs a punch
  • Decaf (8 oz): 2–7 mg — not zero, despite the name

Espresso surprises a lot of people. A single shot has less caffeine than a regular mug of drip coffee. It’s just more concentrated, so it tastes stronger. Two shots (a standard double) get you to about 126 mg, which is more than one cup of drip but less than most people’s morning mug-and-a-half.

Cold brew is the one to watch. Because it’s steeped for 12–24 hours, the concentrate is strong, and many café servings dilute it only a little. A 12-ounce cold brew can easily top 200 mg.

If you’re still working on your technique, here’s a simple guide to how to make coffee at home. And if you measure your grounds by the spoonful, it helps to know how many teaspoons are in a tablespoon.

Espresso shot next to a mug of brewed coffee

What changes the caffeine in your cup

Four things move the number most:

The bean. Robusta beans have roughly twice the caffeine of arabica. Most grocery-store blends are arabica, but cheap diner coffee and many espresso blends mix in robusta — which is one reason that gas-station coffee hits harder.

The grind and brew time. Finer grinds and longer contact with water pull out more caffeine. That’s why French press and cold brew run higher than a quick pour-over.

The serving size. This is the big one people miss. Nutrition labels assume 8 ounces, but almost nobody drinks 8 ounces anymore. Measure your mug once — you might be surprised.

The roast. Dark roast tastes bolder, but it doesn’t have more caffeine. If anything, dark-roasted beans have slightly less caffeine by volume because the beans expand during roasting. By weight, it’s basically a wash.

How much is too much?

The FDA cites 400 mg per day as an amount that’s generally fine for most healthy adults — roughly four 8-ounce cups of brewed coffee. Go past that and you might notice jitters, a racing heart, anxiety, or trouble sleeping. People who are pregnant are usually advised to stay under 200 mg a day.

Caffeine’s half-life is about five to six hours, which means half of what you drank at noon is still in your system at 6 p.m. If coffee keeps you up, try making your last cup before early afternoon and see if your sleep improves.

Frequently asked questions

Does dark roast coffee have more caffeine?
No. Dark roast tastes stronger, but light and dark roasts have nearly the same caffeine when measured by weight. Don’t pick your roast based on caffeine — pick it based on flavor.

Which has more caffeine, coffee or tea?
Coffee, by a wide margin. An 8-ounce cup of black tea has about 47 mg — roughly half of coffee. Green tea has even less, around 28 mg.

How long does caffeine stay in your system?
About five to six hours for half of it to clear, though it varies. Slow metabolizers can feel one afternoon coffee well into the night.

Is decaf really caffeine-free?
Not quite. Decaf still has 2–7 mg per cup. That’s tiny — you’d need about 15 cups to match one regular — but it’s not zero.