Caffeine in Tea: By Type, By Brew, By Cup

Caffeine in tea ranges from 15 to 70 milligrams per 200 millilitre cup depending on class and brew, against 95 to 165 for coffee. The class matters less than most people think: leaf content is similar across types at 20 to 40 milligrams per gram, and the cup varies mostly with how much leaf was used and how long it steeped.

That contradicts a common assumption. Green tea is not low in caffeine and black tea is not high; the leaf chemistry is close, and brewing decides the dose.

The figures by class

The range within a class is wider than the range between classes. A green tea at four grams for four minutes delivers more caffeine than a black tea at two grams for two minutes.

That is why a sensitive drinker should count leaf and time rather than choose a class. Switching from black to green at the same strength changes the dose very little.

The three brewing variables

Leaf quantity is the largest. Caffeine is roughly proportional to dry leaf used, so doubling the leaf doubles the dose, and a gongfu session at seven grams is more than twice a mug at three.

Steep time is second. Caffeine is highly soluble and most of it leaves in the first two minutes, so a longer steep adds little caffeine and a lot of tannin.

Water temperature is third and smallest. Hotter water extracts slightly faster, but the effect is small compared with leaf and time.

That order matters for anyone cutting down. Using less leaf works; steeping shorter is partly effective; cooling the water is not.

• Leaf quantity is the main determinant.
• Steep time matters for the first two minutes only.
• Water temperature has a small effect.
• Reduce leaf first, then time, and ignore temperature.
• Range within a class exceeds the range between classes.
• Switching class at equal strength changes little.

The daily ceiling and how to count

The widely used adult ceiling is 400 milligrams a day and the figure for pregnancy is 200. At 40 milligrams a cup that is ten cups for an adult and five in pregnancy.

The count matters more than the type. A drinker with two coffees and three teas has already reached 400 milligrams, whatever the teas were.

Decaffeinated tea is not caffeine free. It retains two to five milligrams per cup, and the process also removes some catechins.

The half-life is five to six hours, which is why the last cup matters more than the first. A cup at four in the afternoon still has a quarter of its dose in the blood at ten.

Why the tea-class myth persists

The belief that green tea is low in caffeine and black tea is high is repeated everywhere, and it comes from a real observation that has been misread. A cup of green tea often does contain less caffeine than a cup of black tea, but the cause is the brewing rather than the leaf.

Green tea is brewed cooler and shorter, and often with less leaf, because it turns bitter otherwise. Black tea is brewed hotter and longer and often with more leaf. The cup reflects the method.

Brew a green tea at black tea strength and the caffeine is comparable. That experiment is easy to run and it settles the question for most drinkers.

The myth is harmless in itself and it leads people to the wrong conclusion when they are trying to control their intake. Counting leaf is the reliable method.

• The class myth comes from brewing, not from the leaf.
• Green tea is brewed cooler, shorter and lighter.
• Black tea is brewed hotter, longer and heavier.
• Equal-strength brews give comparable caffeine.
• Counting leaf is the reliable method.
• The myth misleads anyone controlling intake.

Caffeine and the theanine balance

Tea also contains theanine, an amino acid that crosses into the brain and moderates the effect of caffeine. The combination produces a calmer alertness than the same dose of caffeine alone.

The ratio varies by tea. A shaded green tea has more theanine than an unshaded one, and a bud tea has more than a leaf tea, which is one reason a silver needle feels gentler than its caffeine figure suggests.

That does not change the caffeine dose, and it does change the experience. A drinker who is sensitive to the jitter of coffee may tolerate the same caffeine from tea.

The practical implication is that counting caffeine is right for sleep and for medical limits, and the theanine is what makes tea drinkable at those doses.

• Theanine moderates the effect of caffeine.
• It produces a calmer alertness than caffeine alone.
• Bud teas and shaded teas carry more theanine.
• Theanine does not change the caffeine dose.
• It explains why tea feels gentler than coffee.
• Count caffeine for sleep, not for feel.

A note on the time of day, which matters more than the total for most drinkers. Caffeine has a half-life of five to six hours, so a cup at four in the afternoon leaves a quarter of its dose at ten.

That is why a drinker who sleeps badly on tea often finds the answer is not less tea but earlier tea. Moving the last cup two hours back does more than halving the dose.

Roughly half the population carries a variant that slows caffeine metabolism, which is why two drinkers with identical habits can sleep differently. A slow metaboliser should move the cut-off earlier rather than drink less.

The practical summary is that the total dose matters for the medical ceiling and the timing matters for sleep, and they are separate questions with separate answers.

• Half-life of five to six hours.
• A cup at four in the afternoon leaves a quarter at ten.
• Earlier tea solves more sleep problems than less tea.
• About half the population metabolises caffeine slowly.
• Slow metabolisers should move the cut-off, not cut the dose.
• Dose answers the medical ceiling, timing answers sleep.

What to do about a caffeine habit

The first step is to count for a week. Most drinkers underestimate their intake badly, because they count cups and not leaf, and a gongfu session counts as one cup in their memory.

The second is to move the last cup earlier. That is more effective than reducing the total for anyone whose problem is sleep rather than anxiety.

The third is to reduce leaf rather than steep time. A shorter steep removes some caffeine and a disproportionate amount of flavour, so the tea becomes weak and no less stimulating.

The fourth is to accept that decaffeinated tea is not caffeine free and to count it if the limit matters. Two to five milligrams per cup is small and it is not zero.

• Count for a week, in grams of leaf rather than cups.
• Move the last cup earlier before cutting the total.
• Reduce leaf rather than steep time.
• Counting steep time removes flavour before caffeine.
• Decaf retains two to five milligrams per cup.
• Sleep problems respond to timing, anxiety to dose.

A final note on the medical limits. The 400 milligram figure is a population guidance, not a personal prescription, and people vary widely in how they metabolise caffeine and how they respond to it. Anyone with a heart condition, an anxiety disorder or a pregnancy should take the figure as a ceiling rather than a target and discuss it with a clinician.

One more comparison that drinkers find useful is with cola, which carries about 30 to 40 milligrams per 330 millilitres. A cup of tea is often comparable per serving and is drunk in smaller volumes, which is why tea is a gentler habit than it appears in the caffeine tables.

The numbers above concern the drink, not the leaf, and that distinction is the whole point of this page.

A last number worth keeping: a 200 millilitre cup of tea at 40 milligrams is roughly a quarter of a 200 millilitre coffee at 130 to 165. That ratio is why tea can be drunk through a day and coffee usually cannot, and it is the most useful single comparison in this area.

Frequently asked questions