Use the amounts suggested for xanthan gum per cup of flour.For example, if you are making cookies with 3 cups of flour, you would add 3/4 teaspoon of xanthan gum.
Baked well
Amount of xanthan gum to use
Cookies
1/4 teaspoon per cup of flour
Cakes
1/2 teaspoon per cup of flour
Muffins and quick breads
3/4 teaspoon per cup of flour
Bread
1 to 1 1/2 teaspoons per cup of flour
Pizza crust
2 teaspoons per cup of flour
If using to thicken liquids, it is best to first make a slurry of the xanthan gum with a small amount of liquid (oil or other fat works best) before incorporating into a larger batch. This will help eliminate clumping.