Your Average Cup. A 12-ounce cup of coffee that you brew at home contains about 100 to 160 milligrams of caffeine. Use a coffee maker with coffee pods and you're likely to get between 75 and 150 milligrams per cup. Instant coffee contains between 135 and 148 milligrams per cup. Purchase that cup at a coffeehouse and you'll get between 178 and 260 milligrams in a 12-ounce serving.