I found out that helium can lift one gram per liter. For example, a balloon filled with one liter helium can lift something that weighs one gram, assuming that the the weight of the balloon and its thread is negligible. But I am very wondered on how many miles from the Earth can a specific balloon can lift a specific item. For example, a balloon which is filled with 1000 liters helium is about to lift an item that weighs 1 kilograms. So meaning the balloon I specified can lift 1,000 grams, or 1 kilograms, which is exactly the weight of the item specified. So, we now know that the balloon I specified can lift the item I specified. But how many miles from the Earth? This is very confusing. I really need the help of everybody. Thank you very much.