Use This Chart for Butter to Olive Oil Conversion and Equivalents
Note that substituting liquid shortening (oils) of any type for solid shortening, like butter or margarine, requires some thought about its end use. Foods that need to stay solid at room temperature, like cake frosting, may not hold their shape if you use olive oil instead. Although mild-flavor olive oils can be used in most cake and pastry recipes, baking will eliminate the aromatic olive oil flavors. Therefore, uncooked sweets such as cake frosting may taste unusual if made with an olive oil. Butter to Olive Oil Conversion is not exactly a one-to-one ratio. Essentially, you need less olive oil when substituting. No further reduction of liquids to compensate should be necessary, just follow the chart above.