How much exposure to the sun gets you an appropriate amount of vitamin d?

10-15 minutes: During the spring, summer, and fall, 10 to 15 minutes of sun exposure between 10:00 am and 3:00 pm is sufficient for adequate vitamin d synthesis in light skinned individuals. Individuals with darker skin require three to six times as much sun exposure as a light-skinned individual to achieve equivalent vitamin d concentrations. For white infants, 2 hours per week fully clothed with no hat.

Depends...: If you're fair skinned, experts say going outside for 10 minutes in the midday sun—in shorts and a tank top with no sunscreen—will give you enough radiation to produce about 10, 000 international units of the vitamin. Dark-skinned individuals and the elderly also produce less vitamin d, and many folks don't get enough of the nutrient from dietary sources like fatty fish and fortified milk.