How much caffeine is in green tea?

An 8 fl oz cup of green tea has 28 mg of caffeine.

That's about a quarter of a cup of brewed coffee, and 7% of the 400 mg a day the FDA cites for most healthy adults.

Source: USDA FoodData Central · checked 10 Nov 2026

When did you have it?

Had at 3 pm, about 9.8 mg is still in you at an 11 pm bedtime. That should not affect most people’s sleep.

Bedtime

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Latest time to drink it

For an 11 pm bedtime, an 8 fl oz cup of green tea stays under the 50 mg most people sleep fine with, even late in the evening. The table works it out for other bedtimes and for how sensitive you are: it is the latest time to start one so that the caffeine left stays under the line all night.

Bedtime	Very sensitive under 25 mg	Average under 50 mg	Not very sensitive under 100 mg
9 pm	Any time	Any time	Any time
10 pm	Any time	Any time	Any time
11 pm	Any time	Any time	Any time
Midnight	Any time	Any time	Any time
1 am	Any time	Any time	Any time

For an 8 fl oz cup of green tea, average clearance (half-life 5 h), 8 hours of sleep. "Any time" means even one at bedtime stays under the line.

How long it lasts

The caffeine from an 8 fl oz cup of green tea peaks in your blood about 75 minutes after you start it, at roughly 24 mg. Half of it is gone in about 5 hours for an average adult; that ranges from roughly 3 to 7 hours, and longer in pregnancy or with some medicines.

Time after	3 hours	6 hours	9 hours	12 hours
Still in you	20 mg	13 mg	8.6 mg	5.6 mg

So one had at 3 pm leaves about 9.8 mg at 11 pm. How long caffeine lasts explains the curve.

How it compares

Green tea is stronger than 38% of the 38 teas we track, by caffeine per serving.

Per fluid ounce (3.5 mg) it is stronger than 66% of them.

To reach 400 mg in a day you would need about 14 of these.

Less caffeine

Gold Peak Chai Tea Latte 25 mg, 14 fl oz bottle
Starbucks Chamomile Mint Blossom Tea 25 mg, Grande
Gold Peak Sweet Tea 20 mg, 16.9 fl oz bottle

More caffeine

Snapple Tea 30 mg, 16 fl oz bottle
Honest Tea Mint Green Tea 35 mg, 16.9 fl oz bottle
Oolong Tea 30 to 40 mg, 6 fl oz cup

Same caffeine: Jade Leaf Matcha, Starbucks Iced Black Tea, Starbucks Iced Green Tea.

FAQ

Is green tea high in caffeine?

No, it is low. An 8 fl oz cup of green tea has 28 mg, which is 29% of the 95 mg in an 8 fl oz cup of brewed coffee.

Can I drink green tea at night?

For most people, yes: even late in the evening an 8 fl oz cup of green tea stays under 50 mg at an 11 pm bedtime.

How long does the caffeine in green tea last?

It peaks about 75 minutes after you start it. Of the 28 mg, about 13 mg is still in you 6 hours later and 5.6 mg after 12 hours, for an average adult with a 5-hour half-life.

Does green tea have more caffeine than a cup of coffee?

No. An 8 fl oz cup of green tea has 28 mg; an 8 fl oz cup of coffee has 95 mg.

Method and limits

The caffeine figure comes from USDA FoodData Central; recipes, brewing and batches vary, so a real serving can differ. The curves use a standard one-compartment model with an average 5-hour half-life and a sleep-friendly line of 50 mg; your own body may clear caffeine faster or slower. How it works has the details.

These are estimates for information, not medical advice.