A single cup of green tea usually won't keep you awake, because it has only about 28 mg of caffeine, roughly a third of a cup of coffee. But it isn't caffeine-free. Two or three cups in the evening, or a strong matcha, can add up to as much as a coffee, and L-theanine, the amino acid in tea often described as calming, doesn't appear to cancel the caffeine out.
Free toolCaffeine Cutoff CalculatorHow much caffeine is still in you at bedtime, and your latest cup.How much caffeine is in green tea?
A typical 8 oz cup of brewed green tea has about 28 mg of caffeine, though it varies with the tea, the amount of leaf and how long you steep it. For comparison:
| Drink | Typical caffeine |
|---|---|
| Green tea, 8 oz | about 28 mg |
| Black tea, 8 oz | about 47 mg |
| Espresso, 1 shot | about 63 mg |
| Brewed coffee, 8 oz | about 95 mg |
| Decaf green tea or herbal tea | little to none |
Longer steeping, hotter water and more leaves all tend to pull out more caffeine. A tea bag steeped for a minute and one left in the mug for ten are not the same drink.
What about matcha?
Matcha is powdered green tea leaf whisked into water, so you drink the whole leaf instead of an infusion. That generally means more caffeine per cup than steeped green tea, and the amount depends heavily on how much powder you use. A thick, two-scoop matcha latte can land closer to a coffee than a cup of tea.
If you like matcha, treat it more like coffee than like tea when you plan your cutoff. Check the label when you can.
Latest time to drink green tea for a 10:30 PM bedtime
Using the site's caffeine math (average 5-hour half-life, aiming for under 25 mg at bedtime):
| What you drink | Caffeine | Latest time |
|---|---|---|
| 1 cup green tea | about 28 mg | 9:40 PM |
| 2 cups green tea | about 56 mg | 4:40 PM |
| 3 cups green tea | about 84 mg | 1:45 PM |
| 1 cup black tea | about 47 mg | 5:55 PM |
| 1 cup brewed coffee | about 95 mg | 12:50 PM |
The multi-cup rows assume you drink them close together. The takeaway: one cup after dinner is usually fine for most people, but a pot through the evening isn't. Different bedtime or a bigger mug? The caffeine calculator works it out.
Does L-theanine cancel out the caffeine?
Probably not in the way people hope. L-theanine is an amino acid found naturally in tea, and it's often described as calming. The research on it is more specific than that.
In two controlled lab studies, volunteers took measured doses of L-theanine and caffeine, alone and together. The combination improved speed and accuracy on some demanding attention tasks. In one of the studies, the combination also lowered "tired" ratings and raised "alert" ratings. In other words, the pairing looked more like focused alertness than sleepiness.
Those studies used isolated doses rather than brewed tea, and they measured focus and mood during the day, not sleep. They don't show that L-theanine protects your sleep from the caffeine in the same cup.
Can green tea help you sleep?
There's a hint that it depends on the caffeine. In a small Japanese study of 20 middle-aged adults, drinking a specially made low-caffeine green tea for a week was linked to lower stress markers than standard green tea, and to better sleep quality in the people who drank more of it. The researchers suggested that caffeine may blunt the relaxing effect of tea's other compounds.
That's one small study, so it's not proof. But it points in a sensible direction: if you want tea in the evening, lower caffeine is the better bet.
Evening tea that won't cost you sleep
- Have your green tea earlier. One or two cups before mid-afternoon rarely matter by bedtime.
- Use one bag and a short steep if you want a cup after dinner.
- Switch to decaf green tea after about 6 PM if you're sensitive.
- Save matcha for the morning.
- Try herbal tea at night. Chamomile, peppermint and rooibos have no caffeine.
- Make the cup part of a wind-down, not a way to keep going. A warm drink fits well in a bedtime routine.
For how caffeine clears hour by hour, see how long caffeine lasts.