Sun Protective Clothing
All clothing offers some sun protection, although some fabrics are better than others at keeping the sun's rays away from your skin. Fabrics are measured with a UPF rating, the higher the rating, the more protection the clothing offers, for example, a UPF rating of 50 means that 1/50 of the UV rays can't make it through the fabric. You want to use clothing with a UPF of 50 or more.
When deciding what to wear outside, the Skin Cancer Foundation says to keep the following in mind:
Tight woven or knitted fabrics offer a high level of sun protection. The smaller the hole between threads, the more UV rays they keep out. If you hold the fabric up to the light and can see through it, then UV rays can get through. Dark blue denim jeans have a UPF of 1,700.
Heavier, denser fabrics keep out the most UV rays. Light fabrics, such as silks and bleached cottons allow UV rays through.
Dark or bright colors are best. These colors absorb the UV rays, keeping the sunlight away from your skin.
Sun Protection Clothing
Today, there are a number of manufacturers who make clothing with sun protection built right into the fabric. Each of these items will have a UPF rating - remember you are looking for a UPF of at least 50. Just as when choosing your own clothes, there are some things to keep in mind when purchasing sun protection clothing:
Obviously, the more area the garment covers, the more sun protection. Long sleeves give you more protection than short sleeves, collars offer more protection than a shirt without a collar.
You want clothing that is comfortable while outside in the sun. Look for clothing that have ventilation and wicking (wicking helps perspiration stay away from your skin) and ventilation increases air-flow helping you feel cool.
Think about the activity you will be doing. Sun protection clothing comes in every-day blouses/shirts, athletic wear, surf/rash shirts and bathing suits. Choose the clothing to go with your activities.
Many people are worried about the extra expense of purchasing sun protection clothing, seeing it as much more expensive than buying a bottle of sunscreen. But, their comparison may be based on using too little sunscreen. It is recommended that adults use at least one ounce of sunscreen every 2 hours while in the sun. That means, for every 6 to 8 ounces you are out in the sun, you should go through about one-half of an 8 ounce bottle of sunscreen. If you are out in the sun everyday, you should be buying 2 to 4 bottles of sunscreen each week. And, that is for one person. Most people, according to the Skin Cancer Foundation, use only a fraction of the correct amount of sunscreen.
Sun protection clothing, however, can be used over and over and may be worth the cost. Each person's needs are different, based on their lifestyle and time spent in the sun.
Creating Your Own Sun Protection Clothing
Another option, SunGuard, is a laundry additive which can make your own clothing into sun protection clothing. According to an article on SeattlePI, SunGuard is manufactured by Phoenix Brands, which also manufactures products like Rit dye, Fab, Ajax and Fresh Start laundry booster.
This product is added to your regular wash cycle and, according to Kathy Dreyer, senior director of sourcing and manufacturing operations at Phoenix Brands, one wash would give your clothing a UPF of 30, a second wash would increase this to 50. Once this is done, the sun protection should last for 20 washes. 
The product is available in some stores, such as Walmart, and is available online. On Amazon, the product is available in a six pack for $24.98, each pack is one treatment.
"Clothing: Our First Line of Defense," Date Unknown, Reviewed by Mona Gohara, M.D., Warwick Morison, M.D, Deborah S. Sarnoff, M.D., Skin Cancer Foundation
 "Indianapolis Company Wages War on Skin Cancer," 2013, June 18, Anthony Schoettle, Indianapolis Business Journal, Seattle PI