Self-rising flour ~ how to convert

Self-rising flour is so popular specially in the UK and US because the correct amount of rising (leavening) agent has already been added to the flour.  Recipes that calls for self-rising flour, usually does not call for baking powder.
Unfortunately self-rising flour can not be found everywhere and we don’t have it here in Norway either.
But converting all-purpose flour to self-rising flour is easy:

* The rule is to add 2 1/2 tsp (2,5) baking powder to each 225 g / 8 oz / 2 cups of plain flour
(1 1/4 tsp baking powder to each 112 g / 4 oz / 1 cup of flour)

You can either measure up while baking or you may want to make it in larger quantity for later use