Dollhouse ratios refer to the proportion between the house and real life, and come in many standard sizes, including 1:6, 1:12, 1:16, 1:24, and 1:48 or in custom sizes. The first number means 1 inch inside the house will be the same as the number of inches the second number is in real life. A 1:12 for example, is called a 1-foot scale because 1 foot—or 12 inches—in real life would be 1 inch in dollhouse land. An 8-foot entryway in real life would be 8 inches inside the house in 1:12 scale—but only 4 inches high in 1:24.
As a general rule of thumb, the bigger the second number, the smaller the house will be, so aim for around a 1:6 or 1:12 for most play dollhouses and 1:24, 1:48, and so on for model miniature work.