Coffee has roughly twice the caffeine of black tea and more than three times the caffeine of green tea. An 8-ounce cup of brewed coffee contains about 96 mg of caffeine, while the same size cup of black tea has 48 mg and green tea has 29 mg.
That said, the gap narrows or widens depending on what type of tea or coffee you’re drinking, how it’s brewed, and how large your cup actually is. Here’s what shapes those numbers in practice.
Cup-for-Cup Caffeine Comparison
The Mayo Clinic’s caffeine data for a standard 8-ounce serving breaks down like this:
- Brewed coffee: 96 mg
- Black tea: 48 mg
- Green tea: 29 mg
These are averages. A strong black tea steeped for five minutes can creep toward 70 mg, while a lightly brewed coffee might land closer to 75 mg. Still, even at the extremes, coffee consistently delivers more caffeine per cup than tea.
Most people don’t drink 8 ounces of coffee, though. A “medium” at most coffee shops is 16 ounces, which pushes the caffeine closer to 190 mg. A large (20 ounces) approaches 240 mg. Tea servings tend to stay smaller or get diluted with milk and ice, so the real-world gap between a coffee shop coffee and a cup of tea is often larger than the per-ounce numbers suggest.
Why Coffee Beans Contain More Caffeine
Caffeine is a natural insecticide that plants produce to ward off pests. Coffee beans simply pack more of it than tea leaves by weight. Arabica beans, the most common variety sold in grocery stores and cafés, contain 1.2 to 1.5 percent caffeine by weight. Robusta beans, often used in instant coffee and espresso blends, contain 2.2 to 2.7 percent. That’s nearly double the concentration of Arabica.
If you’ve ever noticed that a cheap instant coffee or a strong espresso blend hits harder than a single-origin pour-over, Robusta content is a likely reason.
Matcha Closes the Gap
Not all teas are low-caffeine. Matcha, a powdered green tea where you consume the entire leaf rather than steeping and discarding it, delivers about 64 mg of caffeine per cup (using the standard 2-gram serving). That’s nearly identical to a cup of drip coffee made with 10 grams of grounds, which contains roughly 60 mg. Gram for gram, matcha actually has a higher caffeine concentration than coffee, at about 32 mg per gram of powder.
Other high-caffeine teas include yerba maté and certain white teas made from young leaf buds, though neither quite matches matcha’s concentration. If you’re looking for a tea that rivals coffee in terms of a caffeine boost, matcha is the closest match.
Tea’s Caffeine Feels Different
Many tea drinkers report a smoother, more sustained energy lift compared to coffee’s sharper spike and crash. That’s not just perception. Tea contains an amino acid called L-theanine that changes how your body responds to caffeine.
Research shows that combining caffeine with L-theanine improves focus and accuracy at lower caffeine doses than caffeine alone would require. In one study, just 50 mg of caffeine paired with 100 mg of L-theanine improved attention-switching speed and reduced distractibility during memory tasks. Another found that 40 mg of caffeine with about 100 mg of L-theanine boosted alertness and reduced tiredness. For comparison, you’d typically need a much higher dose of caffeine on its own to get those same effects.
This means a cup of black tea with 48 mg of caffeine can punch above its weight in terms of mental clarity, even though the raw caffeine number is half that of coffee. The trade-off is that the stimulation is gentler. If you want a jolt that you feel within 15 minutes, coffee delivers that more reliably.
What Affects Caffeine in Your Cup
The numbers above are averages. Several factors push them up or down:
- Brew time: Steeping tea for 5 minutes instead of 2 can nearly double the caffeine extracted. Coffee brewed in a French press for 4 minutes extracts more caffeine than a quick pour-over.
- Water temperature: Hotter water pulls out more caffeine. This is why cold-brew coffee, despite its long steep time, sometimes has comparable caffeine to hot brew rather than dramatically more.
- Leaf or grind size: Finely ground coffee and broken tea leaves (like those in tea bags) release caffeine faster than whole beans or loose-leaf tea.
- Bean or leaf variety: Robusta coffee beans have nearly twice the caffeine of Arabica. Assam black tea tends to be higher in caffeine than Darjeeling. Shade-grown teas like gyokuro contain more caffeine than sun-grown varieties.
How Much Caffeine Is Safe
The FDA considers 400 mg of caffeine per day safe for most healthy adults. That’s roughly four 8-ounce cups of brewed coffee, eight cups of black tea, or about 14 cups of green tea. A 2017 systematic review confirmed that 400 mg daily is not associated with negative health effects in the general adult population.
In practical terms, most people who drink two to three cups of coffee or four to five cups of tea per day stay well within that limit. Where people run into trouble is combining multiple sources: a morning coffee, an afternoon energy drink, a pre-workout supplement, and a caffeinated soda can stack up past 400 mg without any single source seeming excessive. If you’re sensitive to caffeine or notice jitteriness, heart pounding, or disrupted sleep, switching one or two of those coffee servings to tea is a simple way to cut your intake by half without giving up the ritual.