Can garam masala be used as a substitute for curry powder or vice versa?  Garam Masala also known as all spice powder 
 Garam Masala and Allspice are two completely different things, per the links in this sentence. Garam Masala is often used in curries, usually as a finishing spice.  However, it is not a substitute for the stronger spices needed earlier in most curry dishes, such as the ones in common "curry powder".  Particularly, garam masala usually contains neither turmeric nor hot peppers, two seasonings which are generally considered essential for most "Indian curry" dishes.  