Both gelatin and pectin are thickeners used to make pies, jams, jellies and glazes. Gelatin derives from meat or fish as a by-product of juices released in cooking. Pectin derives from plants and is the substance that gives fruit and vegetable cell walls structure. Replacing gelatin with pectin may not yield the desired texture in the end product. Pectin firms up more than gelatin, which remains syrupy. There is no exact substitution method for the two, so expect to experiment to achieve the best results.
Check the recipe for gelatin and sugar amounts. Some recipes calling for gelatin use honey or artificial sweeteners. Pectin must have sugar to gel properly.
Use 5 cups of sugar for every package of powdered pectin. Use 3.5 cups of sugar for every pouch of liquid pectin. Remove all artificial sweeteners or honey from the recipe.
Prepare the dish as otherwise indicated by the recipe. Add sugar to heated pectin mixes if it isn't thickening as desired.
One package of dry pectin has 325 calories per 100 g. Liquid pectin has 11 calories per 100 g. A 1-oz. gelatin package has 94 calories or 335 per 100 g.