Hi there and thank you for your question!
For most healthy adults, the Food and Drug Administration (FDA) recommends 400mg of caffeine per day - that's roughly 4 to 5 cups of coffee (1). A cup is 8 ounces, which is most likely less than the amount of regular coffee most people pour themselves. Some people are more sensitive to caffeine than others so they can only tolerate a limited amount. However, there are some people who metabolize and break down caffeine faster than others so they can tolerate more.
The FDA has not set a level for children, but the American Academy of Pediatrics discourages children and adolescents from drinking caffeine (1).
If you have a health condition (that includes pregnancy and lactation) and/or taking medication, I encourage you to talk to your doctor or healthcare provider about whether you need to limit your caffeine.
Hope this helps!
Anna Ng, RD
1. "Spilling the Beans: How Much Caffeine is Too Much?" US FDA. Reviewed December 12, 2018. Accessed December 18, 2020. https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much