How Much Caffeine Is in a Glass of Tea? | 40–50 mg Per Cup

You probably know coffee delivers a caffeine jolt. Tea feels gentler, so it’s easy to assume the glass in your hand barely registers on the caffeine scale. That assumption is half-right: tea does have less caffeine than coffee, but the difference is smaller than many people expect.

This article breaks down exactly how much caffeine lands in a typical glass of tea — by type, brew method, and serving size — so you can sip with a clear sense of what you’re getting. No sweeping generalizations, just the numbers and what they mean for your daily limit.

Caffeine by Tea Type

Black tea sits at the high end of the tea caffeine spectrum. Per the Mayo Clinic’s reference chart, an 8-ounce cup of brewed black tea contains about 47–50 mg of caffeine. That’s roughly half the caffeine in an equivalent cup of brewed coffee.

Green tea comes in just below black. A standard cup holds up to 45 mg of caffeine, though individual brands can land anywhere from 25–50 mg depending on the leaf grade and growing conditions. White tea, the least processed, typically delivers 15–30 mg per cup.

Oolong tea sits in the middle ground. Healthline’s comparison data puts its average caffeine content at about 37 mg per 8-ounce serving — close to green tea but slightly less stable across varieties.

Why The Coffee Comparison Surprises People

Most people picture tea as a low-caffeine drink because they compare it to a full mug of coffee. The real picture is more nuanced. Here is how tea stacks up against common coffee servings:

• Black tea (8 oz): 47–50 mg of caffeine. It delivers about one-fourth to one-half the caffeine of an equivalent coffee serving.
• Brewed coffee (8 oz): 95–200 mg of caffeine, depending on the roast and brew strength. Even the weakest coffee cup outpaces black tea.
• Espresso shot (1 oz): 63 mg of caffeine. Ounce for ounce, espresso is far stronger than tea, but a single shot contains roughly the same total caffeine as a cup of black tea.
• Instant coffee (8 oz mug): About 100 mg of caffeine — double the caffeine of an equivalent mug of strong black tea.
• Filter coffee (8 oz mug): Around 140 mg — roughly three times the caffeine of black tea and four times that of green tea.

The takeaway is straightforward: tea is not a low-caffeine beverage; it is a moderate-caffeine one. A single glass contributes meaningfully to your daily intake without the sharper spike coffee can produce.

What Changes the Caffeine in Your Glass

Brewing decisions shift the final caffeine number more than the tea variety itself. Steeping a black tea bag for one minute yields less caffeine than leaving it in for five, and hotter water extracts more from the leaves. According to the caffeine in black tea breakdown from Mayo Clinic, a longer or hotter brew can push black tea to the upper end of its 30–60 mg range, while a quick, cooler steep keeps it near the lower bound.

Matcha changes the math entirely. Because matcha uses whole ground tea leaves rather than steeped leaves, an 8-ounce serving delivers about 70 mg of caffeine — closer to a cup of instant coffee than to standard green tea.

The glass size matters, too. Many tea mugs hold 10 to 12 ounces, not the 8-ounce standard the charts use. A 10-ounce mug of strong black tea can reach roughly 70 mg of caffeine, enough to feel noticeable for caffeine-sensitive drinkers.

Tea Type	Caffeine per 8 oz Cup	Servings to Reach 400 mg Limit
Black tea (standard)	47–50 mg	~8 cups
Black tea (strong brew)	50–60 mg	~7 cups
Green tea	25–50 mg	~8–16 cups
White tea	15–30 mg	~13–27 cups
Oolong tea	~37 mg	~11 cups
Matcha green tea	~70 mg	~6 cups
Decaffeinated tea	5–10 mg	~40–80 cups
Herbal tea (peppermint, chamomile, rooibos)	0 mg	Unlimited for caffeine purposes

The 400 mg figure represents the daily caffeine limit the Mayo Clinic and other health authorities consider generally safe for most healthy adults. Eight cups of black tea or six cups of matcha would bring you to that threshold — a volume most tea drinkers never reach.

Factors That Raise or Lower the Number

To estimate your own glass’s caffeine content, consider these four variables before assuming the standard chart value applies:

1. Brew time. Longer steeping pulls more caffeine from the leaves. A 3-minute steep extracts less than a 5-minute one, and the difference can be 10–15 mg per cup.
2. Water temperature. Near-boiling water (200–212°F) extracts caffeine faster than water at 170–180°F. Green tea is typically brewed cooler, which naturally limits its caffeine yield.
3. Leaf form. Broken leaf tea bags release caffeine faster than whole-leaf loose tea because more surface area contacts the water. The same variety can produce different caffeine levels depending on the cut.
4. Second steep. A second infusion of the same leaves extracts less caffeine — roughly 30–50% less than the first steep, depending on the tea and steep time.

None of these factors make tea a high-caffeine drink by coffee standards. They do mean that two glasses of the same tea type can differ by 15–20 mg depending on how you prepare them.

Tea Versus Other Everyday Drinks

The comparison to coffee is the most common reference point, but tea also overlaps with soda and energy drinks in caffeine content. A 12-ounce can of cola contains about 34–45 mg of caffeine — nearly identical to a cup of green tea and slightly less than black tea. This can surprise people who think of soda as caffeinated and tea as not.

Healthline’s breakdown of caffeine in green tea notes that the L-theanine in tea changes how the caffeine feels. The amino acid promotes calm alertness and slows caffeine absorption, which means the same amount of caffeine from tea tends to produce a milder, longer-lasting effect than the same amount from soda or coffee.

For anyone tracking total daily caffeine from all sources, swapping between tea, soda, coffee, and energy drinks makes a real difference. Two cups of black tea plus one cola adds up to roughly 140 mg — well within 400 mg but enough to matter if you are also sensitive to caffeine later in the day.

Drink	Serving Size	Caffeine Content
Black tea	8 oz	47–50 mg
Green tea	8 oz	25–45 mg
Cola (Coca-Cola, Pepsi)	12 oz	34–45 mg
Energy drink (standard)	8 oz	80–100 mg
Brewed coffee	8 oz	95–200 mg

The Bottom Line

A glass of black tea contains roughly 47–50 mg of caffeine — about a quarter of what is in an equivalent cup of coffee. Green tea is close behind at up to 45 mg, and white tea delivers under 30 mg. Herbal teas are naturally caffeine-free, while matcha pushes higher at around 70 mg per serving. The exact number depends on brew time, water temperature, and leaf form more than most drinkers realize.

Your personal caffeine tolerance, any medications you take, and your sensitivity to afternoon stimulation matter more than any chart number — your doctor or a registered dietitian can help match tea intake to your specific daily limits.