A standard single shot of coffee, specifically espresso, contains about 63 to 64 milligrams of caffeine on average. This amount can vary depending on factors such as the type of coffee bean, roast level, and preparation method, but typically a single shot (1 ounce or 30 milliliters) of espresso has around 63-64 mg of caffeine. Some coffee shops, like Starbucks, may have slightly higher caffeine content per shot (around 75 mg), while double shots obviously contain double the caffeine (~126 mg) or more. Compared to regular brewed coffee, espresso is more concentrated in caffeine per ounce, but a typical cup of drip coffee has more total caffeine due to its larger volume. In summary, the caffeine content in a standard shot of coffee (espresso) is approximately 63-64 milligrams.