Sierra Trading Post offers a chart listing snowshoe sizes. Snowshoe sizing is not based on the size of the wearer's foot, but on her weight. The more a hiker weighs, the longer a snowshoe she requires, while shorter snowshoes are optimal for a lighter hiker.
Unlike sizes for typical footwear, a snowshoe wearer has no single snowshoe size. A hiker can use snowshoes within a range of different sizes based on the sort of performance she wants. Shorter snowshoes weigh less, making hiking faster and less tiring. Longer snowshoes are clumsier and weigh more, but these shoes also provide greater floatation, particularly in fresh or powdery snows.