If you’re a tea drinker, perhaps you’ve wondered how much caffeine you’re consuming each time you finish off a cup. The answer is: It’s complicated. Caffeine content depends on many factors, some of which are within your control as the consumer, and some of which are not. Instead of aiming to calculate the exact amount of caffeine in your tea, it’s more plausible to identify an estimated range of caffeine levels, as well as the relative differences between different types of tea.

As a reference point for coffee drinkers, a double shot of espresso — the typical amount for a latte or cappuccino — contains about 60mg of caffeine. A 12-oz cup of drip coffee has a comparable amount of caffeine.

As prepared with the most common ratios, matcha has the most concentrated caffeine of all teas, because the entire leaf is consumed. One gram (½ teaspoon) of matcha has about 30mg of caffeine. Most people prepare their matcha teas and matcha lattes with 2 to 3 grams of matcha, which means the caffeine in their matcha drink is probably equal to or greater than a typical coffee drink.

The caffeine levels in loose-leaf teas are much more difficult to estimate. Black tea technically has the most caffeine. Black tea has been oxidized longer than other types of the tea, and the oxidation process affects the caffeine content — but only somewhat. Studies have shown the difference in caffeine among loose leaf black, oolong, and green teas to be minimal. But a typical 8-ounce serving of black, green, or oolong tea is likely to fall somewhere in the range of 25mg-55mg of caffeine. How many grams of tea you steep, how long you steep it, and how many times you steep it can all affect the amount of caffeine you consume.

Scientists are confident white tea has considerably less caffeine than the other types, though. White tea is fixed by air-drying, and because that processing method does not include exposure to heat, the caffeine level remains low.

For a completely caffeine-free option, you’ll want to choose an herbal tea. There are countless options available, such as rooibos, peppermint, chamomile, hibiscus, and ginger. These teas are not made with the caffeinated leaves of the Camellia sinensis plant. When choosing among herbal infusions, it’s important to be aware that certain herbals do contain caffeine though, including yaupon, guayusa, and yerba mate.