How much lemon juice equals 1 teaspoon grated peel?

There is no equivalent measure for lemon juice and grated lemon peel. Grated lemon peel is the outer, coloured layer of the rind, while lemon juice is the liquid extracted from the fruit. To obtain lemon juice, you would need to squeeze the lemon, while to obtain grated lemon peel, you would need to grate the outer layer of the rind using a fine grater.