Snowboard boots run true to shoe size, but may vary in fit by brand. The ideal fit for an adult is to have toes brushing the end but not curled while in a standing position. When the boot breaks in and the rider bends their knees and flexes the boot it will draw the foot back so it is no longer touching.
The ideal fit for a kid is to have about a finger's width behind the heel. This allows for room to grow without giving them too much room and a sloppy fit. For more details, check out our Snowboard Boot Sizing Guide.