How much caffeine is in Oolong tea?

A standard 240 ml (8.1 fl oz) cup of brewed oolong tea contains 37 mg of caffeine.

That figure places oolong squarely in the middle of the tea caffeine spectrum — roughly one-third more than a cup of green tea (28 mg) and about one-fifth less than a typical black tea (47 mg). Compared to a 240 ml mug of drip coffee at 96 mg, an oolong serving delivers 0.4 times the caffeine load. The concentration of 15.4 mg per 100 ml makes it a moderate stimulant, enough to sharpen alertness without the rapid spike many people associate with coffee. Because oolong is partially oxidized, its caffeine extraction behaves differently than either unoxidized green or fully oxidized black teas; the leaves release their caffeine steadily over a typical 3–5 minute steep. Most people notice the effects within 15–30 minutes after drinking, with the peak plasma concentration occurring around 45–60 minutes later.

For tea drinkers who want more caffeine than a delicate white tea (16 mg) but less than a robust black tea (47–50 mg), oolong fills a distinct niche. The 37 mg dose also means that a single cup accounts for just 9% of the widely cited 400 mg daily caffeine limit for healthy adults, suggesting that moderate consumption fits easily into a balanced intake. Because the caffeine content is not trivial, however, anyone sensitive to stimulants should be mindful of the timing and total daily cups, especially if oolong is consumed alongside other caffeinated beverages.

How long Oolong tea stays in your system

After you drink a 37 mg cup of oolong tea, your body begins eliminating the caffeine through a first-order metabolic process. The population-average elimination half-life for caffeine is 5.7 hours, meaning that the amount of caffeine remaining in your system halves every 5.7 hours. Using this model, the caffeine remaining at specific time points can be calculated: remaining = 37 × 0.5^(hours / 5.7). At 3 hours after drinking, the amount is approximately 26 mg (37 × 0.5^(3/5.7) = 37 × 0.5^0.526 = 37 × 0.693 = 25.6 mg, rounded to 26 mg). At 6 hours, the remaining caffeine is about 18 mg (37 × 0.5^(6/5.7) = 37 × 0.5^1.053 = 37 × 0.482 = 17.8 mg, rounded to 18 mg). At 9 hours, it drops to roughly 12 mg, and by 12 hours only about 9 mg remain. These numbers are not exact for every individual — liver enzyme activity varies — but they provide a useful reference for gauging how long the stimulant effect persists.

Consider a practical example: if you drink a cup of oolong tea at 15:00, the model predicts that by 21:00 (6 hours later) about 18 mg of caffeine are still circulating. By 23:00 (8 hours later), the remaining amount is approximately 14 mg (37 × 0.5^(8/5.7) = 37 × 0.5^1.404 = 37 × 0.378 = 14.0 mg). Even this modest quantity can interfere with deep sleep for some people, particularly those with a slow caffeine metabolism. The latest cup before bedtime tool lets you compute the cutoff time based on your own sensitivity and target sleep hour. For a 23:00 bedtime, many sleep experts recommend stopping caffeine intake at least 6 hours beforehand, which would mean no oolong tea after 17:00 if you are aiming for a near-zero caffeine level at lights out.

For a healthy adult, the FDA and EFSA regard 400 mg of caffeine per day as a safe total intake. One 240 ml cup of oolong tea at 37 mg accounts for only 9% of that limit. In theory, a person could drink up to 10 cups of oolong tea (400 mg ÷ 37 mg ≈ 10.8 cups) before reaching the 400 mg ceiling, assuming no other sources of caffeine. However, practical daily consumption is rarely that high because of the cumulative volume and the individual’s sensitivity to caffeine. For pregnant individuals, the EFSA recommends a lower daily limit of 200 mg, so a single oolong cup represents 18.5% of that allowance — still a manageable share, but one that requires more careful counting if other caffeinated products are consumed. Adolescents, whose caffeine tolerance is even lower, should follow Health Canada’s guideline of 2.5 mg per kilogram of body weight. For a 50 kg teenager, the daily limit is 125 mg, meaning one oolong cup provides 30% of the safe total.

The timing of oolong tea consumption matters for sleep quality. Caffeine’s elimination half-life of 5.7 hours means that a significant portion of the 37 mg dose remains biologically active for hours after drinking. If you aim for a bedtime of 23:00 and want to minimize the amount of caffeine in your system at that time, the model suggests that finishing your last oolong tea by around 17:00 leaves approximately 14 mg at 23:00 (as calculated in the half-life section). Many sleep experts recommend a caffeine cutoff of at least 6 hours before bed, which for a 23:00 bedtime means no caffeine after 17:00. The latest cup before bedtime tool can compute a personalized cutoff based on your own sleep schedule and sensitivity. Even a small amount of caffeine at bedtime can reduce total sleep time and increase nighttime awakenings, as documented by the 2013 study by Drake et al., which found that 400 mg of caffeine consumed six hours before bed still disrupted sleep significantly. At 37 mg, the effect is milder, but cumulative exposure from multiple teas or other sources can produce a similar outcome.

If you are particularly sensitive to caffeine — experiencing jitters, anxiety, or palpitations even at low doses — you may want to limit oolong tea to the morning hours or switch to a decaffeinated version. The safe daily limit by body weight calculator provides a more individualized estimate of your maximum caffeine intake, and the caffeine half-life calculator lets you model the decay of multiple doses across the day. Remember that oolong tea is often consumed in multiple infusions of the same leaves, and the second and third steeps typically contain less caffeine (roughly 40–60% of the first steep), so you can modulate your intake by re-steeping rather than using fresh leaves each time.

Within the tea family, oolong tea’s 37 mg of caffeine per 240 ml positions it as a middle-tier option. It carries more caffeine than white tea (16 mg) and green tea (28 mg), but less than the classic black teas: standard black tea at 47 mg, English Breakfast at 50 mg, and Earl Grey also at 47 mg. This ladder illustrates the general rule that caffeine content tends to rise with oxidation level, though processing methods blur the boundaries. For a more substantial caffeine boost, matcha — made from powdered green tea leaves and prepared as a suspension rather than an infusion — delivers 70 mg per 240 ml, nearly twice the oolong dose. On the other hand, bottled iced tea (45 mg in 355 ml) has a lower concentration per 100 ml (12.7 mg) than oolong (15.4 mg), so a typical iced tea serving may actually contain less caffeine per sip than a hot oolong.

When compared to coffee, oolong tea is unmistakably milder. A 240 ml cup of drip coffee contains 96 mg of caffeine, which is 2.6 times the oolong amount. A single espresso shot (30 ml) packs 63 mg, so even that small volume delivers 70% more caffeine than a full mug of oolong. Energy drinks present an even starker contrast: a 250 ml can of Red Bull contains 80 mg, and a 473 ml Monster Energy can hits 160 mg. For someone who typically drinks coffee and wants to reduce caffeine intake without eliminating it, switching to oolong tea can cut the per-cup dose by about 60%. The black tea caffeine page and green tea caffeine page provide detailed comparisons within the tea category, and the site’s drink comparison tool can line up oolong against any other drink in the dataset.

For those who enjoy the flavor of tea but need to manage their caffeine carefully, oolong occupies a practical middle ground. It offers more alertness than a gentle green tea without approaching the caffeine load of a strong black tea, and at 37 mg it remains well below the 50 mg threshold that many people use as a cutoff for a mild stimulant effect. The 9% share of the daily 400 mg limit means that a second cup later in the afternoon still leaves plenty of room for other caffeinated foods or beverages, provided total intake is monitored.

What changes the number for Oolong tea

The 37 mg figure for a 240 ml cup of oolong tea is a representative average derived from laboratory analyses of multiple brewed samples. In practice, the caffeine content of your cup can vary significantly based on several factors. The most important variables are the oxidation level of the oolong leaves, the water temperature, the steeping time, and the leaf-to-water ratio. Oolong teas span a wide range of oxidation — from 10% to 70% — and the degree of oxidation influences how readily caffeine extracts during brewing. Lightly oxidized oolongs, such as Tie Guan Yin, tend to release caffeine more slowly than heavily oxidized, dark-roasted oolongs like Wuyi Rock tea. Published values for oolong tea caffeine range from about 30 mg to 50 mg per 240 ml, so the 37 mg value is a midpoint that reflects common brewing conditions.

Steeping time is a particularly powerful lever. The standard 3–5 minute steep used in most laboratory tests extracts the majority of available caffeine, but a quick 1-minute infusion might yield only 20–25 mg, while a longer 10-minute steep could push the total above 45 mg. Water temperature also matters: boiling water extracts caffeine more efficiently than water at 80°C, which is often recommended for delicate oolongs. The amount of leaf used per cup — typically 2–3 grams — can change the final caffeine content by 30% or more. To illustrate the effect of these variables, consider the following range of typical scenarios:

• A 1-minute steep with 2 grams of leaf in 80°C water: roughly 20 mg of caffeine.
• A 3-minute steep with 2.5 grams of leaf in 95°C water: approximately 35–40 mg.
• A 5-minute steep with 3 grams of leaf in boiling water: up to 50 mg.

Decaffeinated oolong tea is available but not completely caffeine-free. The decaffeination process typically removes 95–98% of the caffeine, leaving a residual 1–4 mg per 240 ml cup. If you are strictly avoiding caffeine, herbal teas (0 mg) are the safer choice. The variation in published caffeine values for oolong is also influenced by the tea cultivar, growing conditions, and processing methods. Because no single number can capture all possibilities, the 37 mg reference serves as a reliable baseline for a standard home-brewed cup, and the page’s calculator allows you to adjust the dose to match your personal brewing habits.

Finally, it is worth noting that commercial bottled oolong teas often contain different caffeine levels. A 240 ml bottle of mass-market oolong may list only 20–30 mg due to dilution and processing, so always check the label. Our data are based on freshly brewed loose-leaf oolong prepared according to typical consumer instructions, making them directly applicable to what you prepare at home or order in a café.

Where this figure comes from

The 37 mg caffeine value for a 240 ml cup of oolong tea is sourced from the USDA FoodData Central database, which compiles laboratory analyses of commonly consumed foods and beverages. The specific entry reflects a composite of brewed oolong tea samples prepared under standard conditions: 2–3 grams of loose-leaf tea steeped in 240 ml of near-boiling water for 3–5 minutes. Because brewing practices vary, the USDA and other authoritative sources often report a range rather than a single number; for oolong tea, typical published values span 30–50 mg per 240 ml. Our choice of 37 mg as the representative figure is based on the median of multiple peer-reviewed analyses and aligns with the values reported by the Mayo Clinic and other health organizations. We update our dataset when new, high-quality data become available, and the entire dataset is open for inspection on the open caffeine dataset page where anyone can review the raw numbers, suggest corrections, or compare with other sources.

Why do different sources sometimes disagree on the caffeine content of oolong tea? The main reasons are the natural variability of the tea leaves themselves, differences in the brewing protocol used in the laboratory, and the method of caffeine measurement (HPLC versus spectrophotometry). Even the same brand of oolong can yield different caffeine levels from one harvest to the next. This transparency is exactly why we present a single reference value alongside a clear explanation of the factors that can move it. If you have a peer-reviewed or official source that contradicts our figure, we welcome the contribution so that the page can better reflect the best available evidence.

Bottom line

Oolong tea, brewed from partially oxidized leaves, delivers 37 mg of caffeine in a standard 240 ml (8.1 fl oz) cup. That is equivalent to 15.4 mg per 100 ml, or about 0.4 times the caffeine of a typical 240 ml drip coffee (96 mg). The dose accounts for 9% of the 400 mg daily limit for healthy adults, so a single serving is a modest addition to a day’s total. The caffeine content is higher than that of green tea (28 mg) and white tea (16 mg), but lower than that of black tea (47 mg) and matcha (70 mg). Because oolong’s caffeine is released gradually during steeping, the exact amount in your cup depends on how long you brew it and the temperature of the water. For most people, a morning cup of oolong provides a gentle, sustained alertness, but if you are sensitive to caffeine or aiming for a caffeine-free period before bed, you should finish your last cup at least 6 hours before sleep. The individual variation means that the 37 mg figure is a reliable starting point, not a universal constant.

Should you need to tailor the numbers to your own habits, the tools on this site let you calculate the decay of caffeine in your body, estimate your personal daily limit, and compare oolong against any other drink in the dataset. The underlying data are open and sourced from the USDA, so you can trust the transparency behind the numbers.