How Much Caffeine Is in Your Tea

The box says 25 mg. The next box says 75. Both are green tea. Neither is wrong.

Tea is annoyingly hard to pin down on caffeine, and tea writing usually fakes confidence it has not earned. Here is the actual picture, with the uncertainty left in.

The spread

Published measurements of caffeine per serving span a wild range. For the same category. Sometimes for the same tea.

Notice how much the bars overlap. A strong green can out-caffeine a weak black. Matcha is not in a different league, it is at the high end of the tea league. None of the categories are clean.

Six things move the number

Roughly in order of how much.

Cultivar. The tea plant comes in two main varieties. Camellia sinensis var. sinensis (small-leaf, Chinese) is used for most greens, oolongs, and whites. Camellia sinensis var. assamica (large-leaf, Indian) is used for Assam, Ceylon, Dian Hong, and most puers. Assamica plants carry more caffeine than sinensis plants. This is genetic, and it is probably the biggest single driver.

Leaf age. Tips and buds hold more caffeine than mature leaves. Silver Needle is all buds. Jin Jun Mei is all buds. Both are punchy. A summer pluck of coarse leaves from the same bush makes a milder cup.

Shading. Gyokuro and matcha are shaded for several weeks before harvest. The lack of sunlight pushes the plant to accumulate amino acids (which is why those teas taste sweet and savoury), and in most studies it raises caffeine a little as well. The popular intuition that shading produces a gentler cup is wrong in the direction that matters: shaded teas are more concentrated, not less.

Processing. Most processing steps (steaming, pan-firing, oxidation, fermentation) leave caffeine largely intact. Roasting is the exception. Heavily roasted teas like houjicha (roasted Japanese green) and traditional Wuyi yancha lose some of their caffeine to the roast. This is why houjicha is the classic evening-friendly green, and why a deeply roasted oolong tends to feel less wiring than its unroasted cousin from the same bush.

Brewing. Hot water, long steep, more leaf: more caffeine. The first infusion pulls the majority of it out. By the third, most of the caffeine is already in your stomach.

Particle size. With loose leaf, you steep and throw the leaves away. With matcha, you drink the leaf. With teabag dust (CTC black), surface area is massive, and extraction is fast and hard.

For scale, coffee

People often ask how tea compares to coffee. The rough picture:

Tea has range. That range tops out below coffee's middle. If you are replacing coffee with tea to cut caffeine, you will cut it, even with matcha.

Why it feels different from coffee

Most tea drinkers describe tea as coffee but calmer. That is a useful shorthand, but not quite what is happening. Caffeine makes you alert, and that part is the same in both drinks. What differs is the texture of everything around the alertness.

Tea also contains L-theanine, an amino acid almost unique to the tea plant. L-theanine crosses into the brain and promotes alpha-wave activity, the pattern of relaxed wakefulness that shows up during meditation. It does not pull you back down from the caffeine. It sits alongside the caffeine and takes the edges off.

A useful way to think about it: caffeine produces a signal, and L-theanine smooths the signal. You still get alert. You just do not get the spikes, the anxiety, and the eventual crash. Controlled trials on the combination have measured what tea drinkers have long described: faster attention-switching, steadier alertness, softer decline.

The full picture is still being worked out. Behavioural trials usually dose L-theanine at 100 to 200 mg, while a cup of black tea contains around 24 mg and a cup of green around 8. Whether a single cup reliably produces the effect that laboratory doses produce is a real open question, and honest writing should name it rather than dodge it.

Tea also contains catechins, a family of polyphenols that includes EGCG. In laboratory assays, EGCG has been shown to weakly bind the same brain receptors that CBD and THC in cannabis act on. The amount reaching the brain from a cup of tea is probably too low to produce any cannabis-like effect, and the single study behind this finding has not been independently replicated. But it hints that tea compounds touch more of the brain’s signalling systems than the caffeine-and-L-theanine story alone suggests.

The direction of the synergy effect across studies is consistent, and it is part of why some people who cannot tolerate coffee are fine with tea. Tea drinkers have their own names for the state. “Calm focus” is one. The more colourful one, saved for the quiet lingering feeling several infusions into a session, is “tea drunk.” We have a longer piece on that state, and the mechanisms behind it. English and Chinese also name tea differently, and we wrote about how that plays out in tasting.

Tuning your cup

If you are sensitive to caffeine, you have a lot of levers. You do not need decaf.

Drop leaf amount first. Cooler water second. Shorter steeps third. And remember: by your third or fourth infusion, most of the caffeine is gone, but the L-theanine tends to keep extracting. The later infusions are where tea drunk lives.

The number on the box is a guess. What matters is the leaf, the water, and you.