How much baking powder to add to plain flour to convert to sr?

[extremelychocolateymilkroll]

and does it matter what you're making - eg a sponge or biscuits? TIA

It usually says on the baking powder packet.

Wiki Says - "Here are a few versions of making SR Flour:
? 500 gm. plain flour + 2 1/2 tsp. baking powder + a pinch of salt
? 500 gm. plain flour + 20 ml. cream of tartar + 10 ml. bicarbonate of soda
? 1 cup plain flour + 1 1/2 tsp. baking powder + 1/4 tsp. salt
? 225 gm. plain flour + 2 level tsp. baking powder
? 450 gm. or 16 oz. plain flour + 1 oz./25 gm. baking powder
? 1 cup plain flour + 1 1/4 tsp. of baking powder.
Some cooks suggest a half teaspoon of baking powder per cup of flour.

Pretty confusing!

Thanks QueenOf. Would never have thought of looking there. It says 4tsps bk pwd to 225g plain flour. Some searches I did on Google seemed to suggest that you would need to put different amounts of bk pwd in if you were making a sponge or biscuits. Has anyone heard of this?

Thks v much for looking Stirling - as you say, pretty confusing!

I did one tsp to 125g flour to make some cupcakes last week and it was fine, maybe slightly too much if anything.