When exposed to sunlight, your skin produces vitamin D. How much you create depends on your skin type, time in the sun, and how much skin is exposed. We can estimate this using two simple steps. First, we calculate how much vitamin D your skin makes per square centimeter per minute based on UV radiation and daylight hours. Then, we adjust that number for how long you’re outside, how much skin is exposed (like arms, legs, and face), and your skin type. For example, exposing 5,000 $cm^{2}$ of skin to the sun for 30 minutes will produce more vitamin D if done around noon when UV rays are strongest. Always avoid sunburn!