The Short Answer:
Here is a general guideline for how much the average cup of tea will have:
The Long Answer
Black tea, green tea, oolong tea, and white tea all contain caffeine. It’s commonly believed that black tea has the highest caffeine content while green and white tea has the lowest caffeine content. However, this isn’t always true.
Oxidation Doesn’t Affect Caffeine Content
What makes a green tea different from a black tea? Oxidation. All teas start from a freshly plucked leaf. It’s all about how long they’re allowed to sit out and naturally break down. During this process, the caffeine content remains the same. So the same leaf made into a green or a black tea will have the same caffeine.
What Affects Caffeine Content in Tea?
- Steeping Time: The longer you steep a tea, the more caffeine you get. That’s part of the reason why black tea tends to have more caffeine, because it steeps longer than green or white tea.
- Steeping Temperature: The hotter the water, the more caffeine gets in your pot of tea.
- Size of Harvested Leaf: Tea buds have the highest caffeine content. The lower leafs on the tea tree have lower caffeine. Guess what teas generally use the most tea buds? White teas and premium grade teas. Check out this article to see a fun graphic on how much caffeine is in each part of the leaf.
- Fineness of Finished Tea: Some teas like oolongs have broad leaves when steeped. However, many breakfast teas have a broken leaf. Broken tea leaves lead to more caffeine getting released in your cup of tea.
- Shading: A shade grown tea like Gyokuro will have a higher caffeine content than a tea grown in full sun.
- Assam vs Chinese varieties: Indian Assam varieties of tea tend to have more caffeine than Chinese varieties.
- Time Harvested: Tea harvested in warm months tends to have higher caffeine than teas grown in the cooler months.
- Multiple Infusions Reduces Caffeine: To see how much caffeine is removed per infusion, check out this article with a fun graphic.
- Too Easy to be True: De-bunking the At-Home Decaffeination Myth. Bruce Richardson http://elmwoodinn.com/about/caffeine.html
- Caffeine Intake by the US Population. FDA. http://www.fda.gov/downloads/AboutFDA/CentersOffices/OfficeofFoods/CFSAN/CFSANFOIAElectronicReadingRoom/UCM333191.pdf
Fun Fact: Did you know that on average, the caffeine in 2 cups of tea equals 1 cup of coffee? Source: FDA