Place ginger in a medium, heavy-bottomed saucepan. Add enough water to cover by 1 inch. Partially cover saucepan and bring to a boil over medium-high heat; boil until ginger is almost cooked through but still slightly al dente, about 1 hour. Drain.
Weigh cooked ginger and return it to saucepan with an equal amount of sugar. Add 2 tablespoons water; bring to a boil over medium-high heat, stirring, until ginger becomes translucent, about 20 minutes.
Reduce heat and continue cooking, stirring, until ginger is crystallized and begins to clump in the middle of the pan.
Meanwhile, sprinkle a large rimmed baking sheet with sugar. Pour crystallized ginger onto prepared baking sheet and roll in sugar, separating pieces. Transfer to a sterilized jar and store in a cool place for 3 to 6 months.