A standard 12-oz can of Coca-Cola contains 34 mg of caffeine.

A 12-fl-oz can of Diet Pepsi has 35 mg of caffeine, and bigger bottles scale up with the serving size.

A standard 20-oz Dr Pepper bottle lists 68 mg of caffeine, while a 16.9-oz bottle lists 58 mg.

A 20-oz Coca-Cola Original bottle has 57 mg caffeine; a 12-oz can has 34 mg.

A 12-ounce brewed coffee often sits near 140–150 mg of caffeine, with many cups landing from 110 to 250 mg.

Two espresso shots often land around 120–150 mg of caffeine, with real cups drifting up or down based on dose, bean, and shot style.

Most people notice caffeine at 50–100 mg, with a clearer lift near 100–200 mg when taken on an empty stomach.

An 8-oz cup of brewed coffee often has about 96 mg of caffeine, with many cups falling between 60 and 150 mg.

Most adults feel more alert with 50–200 mg caffeine taken early, while keeping total daily intake at or under 400 mg.

Most healthy adults can have up to 400 mg caffeine a day, with lower limits in pregnancy and for teens.