The gist: Coffee generally has more caffeine than Green Tea Factory, but certain factors can affect this, and in some cases, it can be the other way around. Different factors, both within and outside the control of the drinker (e.g. brewing method and time vs tea variety/coffee species) affect the caffeine levels in the final brew.

The effects of caffeine can be felt faster in coffee since it has a higher caffeine content, but green tea has the added benefit of having L-theanine, which has a calming effect.

Which Has More Caffeine — Tea or Coffee?

Coffee generally has more caffeine than green tea. Based on the FDA’s estimate, an 8 oz cup of coffee typically contains 80 to 100 mg of caffeine. In contrast, an 8 oz cup of green tea typically has 30 to 50 mg of caffeine.

Naturally, there are deviations to this since there are factors that can affect the caffeine content in both tea and coffee. Some coffees have more caffeine than others in the same way that some teas also have a higher caffeine content than others.

Factors That Affect the Caffeine Content in Green Tea

Tea Variety — The caffeine content in tea varies depending on the variety.

Harvest Time of Leaves — The harvest season of tea leaves can also affect caffeine content, with earlier harvests of the same plants having a higher caffeine content.

Temperature — The higher the temperature, the more caffeine is extracted into the brew.

Brewing Time — Longer steeping/brewing will yield more caffeine. However, brewing time is related to temperature since hotter water will also extract caffeine faster into the brew. This is why cold-brewed tea, while steeped longer, will still have less caffeine than hot-brewed tea.

Brewing Method — Also related to temperature, cold-brewing extracts less caffeine into green tea than hot brewing. Iced tea, however, is generally brewed hot and then iced to cool down, so it has as much caffeine as a normal hot brew.

*Based on analyses by Eurofins Scientific Inc.

Factors That Affect the Caffeine Content in Coffee

Coffee Species and Grind Size — Arabica has a lower caffeine content than Robusta. The grind size of the coffee also has an effect on caffeine content, with finer grinds releasing more caffeine.

Brewing Method — Between the brewing methods, such as drip coffee, percolator, and French press, and the espresso method, brewed coffee has been found to have more caffeine perserving. This is based on the typical serving sizes for espresso (1 oz/shot) and brewed coffee (8 oz/cup).

Amount of coffee used — More coffee that goes into the brew also means a higher caffeine content.

Brewing Time — Another factor that affects how much caffeine is in coffee is the brewing time — the longer the brewing time is, the more caffeine is extracted.

Temperature —More caffeine is extracted into coffee brewed using higher temperatures. This is why cold-brewed coffee has a lower caffeine content than hot-brewed coffee.

Decaf Green Tea vs Decaf Coffee

Most people probably know about decaf coffee but decaf green tea is a little harder to find. However, much like decaffeinated coffee, decaffeinated green tea also isn’t completely caffeine-free, although its caffeine content is significantly lower. Typically, the remaining caffeine content is 5%~15% of the original beans or leaves.