Knowing when a cupcake is done is not always easy. Every batter is different and every oven has its issues. I usually bake cupcakes for 12 minutes and then check them every minute after that. I don't use "the cupcake is done when you insert a toothpick and it comes out clean" method because this almost always guarantees you a dry hunk of cake. I like to take them out of the oven just before they are done because they continue to cook for a few minutes.
This kitchen timer from Bright & Bold will make sure your cupcakes come out of the oven right on time!
Cupcake Kitchen Timer