A single tablespoon of fresh ginger root is equal to one-fourth of a teaspoon of dried ginger. Crystallized ginger can also be substituted for fresh ginger once the sugar is washed off, where one-fourth a cup of minced crystallized ginger is equal to a tablespoon of fresh minced ginger.
Ground ginger is not the best substitute for fresh ginger, as it loses much of the spicy, pungent flavor of fresh ginger when dried and ground. Whole dried ginger works a little better, as it retains more of its flavor. Green ginger and galangal can also be used to replace fresh ginger in a recipe, though these change the overall flavor slightly.