How do I know if a hat or visor provides adequate sun protection?
To check a hat or visor for sun protection, do this test: put on a hat and stand under direct sun. Ask someone to check or photograph your face from all angles. If the sun is hitting parts of your face, then you are vulnerable to sun damage and skin cancer. Unless your face is very very very small, you will likely find that a a 3-inch hat brim is not enough. A 4-inch brim is much better and probably a 5-inch hat brim is best (although not always attractive, so you should make the choice that balances your priorities).