Yo! Check the sides of the heel. There should be a number in millimeters (mm). That should help figure out the next size up. A better idea (if you have the time) is to take these pups to a good ski shop and have a boot fitter take a look. You may need just a small adjustment to these boots instead of a whole new size. Ski boots rarely fit comfortably straight out of the box and 'too small' may be 'spot on' once they are broken in properly. For myself, I have a size 8.5 or 9.0 street shoe and go down two sizes or so in ski boots. Sucks to watch TV in 'em, but perfect for arcing big skis thru deep snow! Hope this helps some!---Imparting my wisdom--- You don't need a small boot. Plain and simple. The best boot for you, is the most comfortable boot for you too. No one likes skiing uncomfortably. My boots are comfortable enough to watch TV in, Check them out, FULL TILT BOOTS... www.fulltiltboots.com