Say birkat ha'mazon instead of al ha'michya if you ate enough bread-like foods (mezonot) or bread-like food combinations (such as crackers with tuna salad) to be the volume of your normal biggest meal of the day. This is true even if:

• You had not planned to have a meal (for example, you planned to eat only one slice of pizza but then ate two more), and
• Did not wash your hands before the meal.