The answer is yes – you can use all purpose flour instead of cake flour but you have to make some adjustments.
Cake flour has less protein and is a finer grind than all purpose flour. It is also bleached using chlorination so fat adheres to it better and air bubbles are more evenly dispersed. All that adds up to a finer, lighter crumb in your baking.
Cake flour is also lighter in weight than all purpose flour so if you are measuring by weight all purpose flour is about 12% heavier than cake flour.
If you want to substitute all purpose flour for cake flour:
- for each cup of cake flour take 1 cup of all purpose flour and replace 2 Tbsp of the all purpose flour with 2 Tbsps of corn starch.
or
If you want to substitute cake flour for all purpose flour:
- for each cup of all purpose flour called for use 1 cup + 2 Tbsps of cake flour.