How to convert plain flour to self-raising?

I need to use 125g of self-raising flour and don't have time to get some. Do you know how much baking powder I have to add?How to convert plain flour to self-raising?
a table spoon to 2 cups of flowerHow to convert plain flour to self-raising?
For each cup of all-purpose flour, add 1 1/2 teaspoons of baking powder and 1/2 teaspoon of salt.