Commercial US apple pie is about 52% water by weight.
The percentage comes from the nutrition profile for commercially prepared apple pie: a 100 g portion contains about 52.2 g of water. The rest is chiefly carbohydrate, fat, and a smaller amount of protein, supplied by the apples, pastry, sugar, and shortening or butter.
“52% water” does not mean the pie is watery. Fruits naturally contain substantial water, and apples contribute much of it. Baking removes some moisture, but the filling and other ingredients still leave over half of the finished product’s mass as water.
This value describes a commercial US product, not every apple pie. A homemade pie with a different apple variety, crust, filling ratio, or baking time can have a different moisture percentage. The figure also explains why calories must be interpreted alongside serving size: water adds weight without adding food energy.