Oil gives boxed cake mix a moist consistency that makes it taste almost handmade. If you don't have any oil on hand or just don't like using oil, then it's possible to substitute butter in the recipe. Butter contains a high fat content, just as oil does, and gives the cake mix a slightly different flavour and texture. When you replace oil with butter in a boxed cake recipe, you should use the same ratio of butter as you would oil.
Read the instructions on the boxed cake mix carefully and note the amount of oil the recipe calls for.
Measure the butter, following the sizing amounts listed on the side of the butter stick. Transfer the butter to a small bowl.
Place the bowl in a microwave and cook for ten seconds. Stir the butter lightly with a spoon and place back in the microwave for ten more seconds. Repeat the process until the butter is completely melted.
Follow the package instructions, placing the necessary ingredients in a large bowl. Pour the melted butter into the recipe and mix until combined.
Bake the cake mix according to the package guidelines. The cake is done when a toothpick inserted into the middle comes out clean.
If you're using butter from a tub, then scoop out the proper amount using a measuring cup. Place the butter into a small bowl and microwave as directed.