The answer to this question largely comes down to your local climate and personal preference, and might even require a little bit of experimenting to find the magic number. A good rule of thumb is to sleep with two blankets, one thicker than the other. You can add on a third if needed for colder nights, or remove one on hot summer nights. The important thing is to achieve the right temperature that enables you to sleep undisturbed throughout the night. As long as you aren’t waking up sweating or shivering, you’re probably sleeping with the right number.