Because mushrooms have such a high water content (around 92%), the ratio you need when reconstituting dried mushrooms is somewhere around 9:1. However, when trying to substitute fresh mushrooms for dried and reconstituted, it works out somewhere around 5:1/6:1. - For every 1lb/450g of fresh mushrooms that a recipe calls for, use about 3oz/85g dried (and then reconstituted) - 1 cup fresh mushrooms = 1/3 oz/10g dried (then reconstituted) - 1Tbsp powdered mushrooms = around 4oz/110g fresh mushrooms.