Helmets for small adult heads
Many adults have smaller heads than the norm, but there are always helmets available in your size. You might have to use a "youth" or even a "child's" model, but they come in adult styles.
If you are looking for an XXS helmet for a baby, our page on tiny helmets for infants has more on that.
You can use a youth or even child helmet
Ever shop for clothing in the child's section? For a very small head, you can use a youth or child helmet if it is the one that fits you well. All of them pass the same impact standard, with helmets for children under five providing extra coverage. Many manufacturers have "women's" helmets as well, and those are sized in medium down to extra small. They fit a man just as well as a woman if that is your head size, and many have nicer graphics.
Younger riders want fashionable helmets too, so many manufacturers have helmets for them that are styled like larger adult helmets. You may have to look a little longer, but you can find something to fit.
You can check our latest page on helmets for the current season for the size ranges of many manufacturers.
Making a helmet smaller
First, you will always get a better fit with a helmet that is sized for your own head. Loose or sloppy fit means the helmet may not be between you and the pavement when you actually arrive. For ring-fit helmets, you cinch up the fit ring as tight as it will go, of course, but if it doesn't provide a snug fit you have to go to another model. For pad fit helmets, you have to reduce the helmet's size with thicker fitting pads. The thicker fitting pads do not detract from the protection of the helmet, as long as they hold it in place well. That is their function, since the harder crushable foam in the helmet is actually the part that manages the impact energy. You may have to experiment with firmer pads to make sure that the thickness does not make the helmet unstable on your head. Then carefully adjust the fitting foam to touch all the way around your head but not be too tight, and adjust the straps for maximum stability to hold the helmet level on your head while still not too tight for comfort. Be prepared for the helmet to look very large on your head. Here is a page that explains why it can't be thinner.