Although definitions vary, a traditional cappuccino generally features one or two shots of espresso, an approximately equal amount of steamed milk and rich, creamy foamed milk to fill the mug. A dry cappuccino uses less milk than espresso and a wet one includes slightly more milk than espresso. Exact quantities differ because the drink is made to taste. However, if you add more steamed milk than foam, you're not making a cappuccino at all -- it's a latte.
Prepare one or two shots of espresso in your espresso machine according to the manufacturer's instructions. Pour the espresso into a mug and set it aside.
Fill the milk pitcher one-third of the way with whole milk to leave plenty of room for the liquid to expand.
Turn on the espresso machine's steam wand for a second to expel any moisture inside, then turn it back off. Slide the wand into the milk pitcher, fully submerging the tip, and turn it back on.
Slowly lower the milk pitcher until the tip of the steam wand is flush with the surface of the milk. When it's perfectly positioned, listen for the distinct foaming sound as the surface of the milk begins to rise and turn to foam. Continue slowly moving the pitcher as needed to maintain the foaming process.
Steam the milk until it reaches about 150 degrees Fahrenheit on the machine's thermometer, or use an instant-read thermometer. Turn off the steam wand and carefully maneuver the milk pitcher away from the wand.
Hold back the foam with a spoon as you slowly pour liquid steamed milk into the mug of espresso. Pour just a quick splash for a dry cappuccino or use a longer pour for a wet one. Precise measurements aren't important; it's all about your personal taste.
When you're happy with the amount of milk, use the spoon to scoop foam into the mug until it's full.