First off, all three of these products are derived from the same source - animal collagen. When heated slowly, collagen in the skin, bones, and connective tissue of an animal breaks down into gelatin, which can then be used to set liquids into jellies.
Gelatin powder is gelatin that has been dried and broken up into individual grains, which has the advantage if dispersing more easily throughout a dish. Gelatin sheets are made from gelatin that is dried in a flat sheet. Sheets result in a clearer, more transparent final product than powder. As far as we could tell from our research, gelatin sheets and gelatin leaves are just different names for the same product.
Since these are all the same product, you'd think that substituting them would be simple! Apparently, this is not so:
In culinary school, we were taught that one tablespoon of powdered gelatin equals 4 gelatin sheets. If you're in the United States buying standard grocery-store gelatin (usually Knox), this should be fairly safe substitution ratio. You can also go by weight, which is typically 7 grams of gelatin per cup of liquid to be set according to On Food and Cooking.
If you're outside the US or using different products, the relative strength of the gelatin products might be different. In these cases, it's best to follow the instructions on the box. These instructions usually give the amount of gelatin to be used per cup of liquid, and they assume that you want a firm final product (not soft and not completely stiff). You'll need to do a little math with your recipe to figure out how much liquid you're working with, but there is no danger in substituting your gelatin for whatever is called for in the recipe.
We think the best plan is to find a source for gelatin and stick with it. The more you work with it, the more you'll understand how it works and be able to make adjustments on the fly. If you think your final product is too soft or stiff, make a note to change the proportion of gelatin the next time. Remember also that foods with gelatin get stiffer the longer they sit, so a bavarian that was creamy right out of the fridge will be rubbery two days later no matter what kind of gelatin you use.
• For more info, check out our post on How to Work with Gelatin.
Are any of you gelatin-experts? What other advice do you have about substituting and working with various forms of gelatin?
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