Convert plain flour to self-raising flour with baking powder.

We've all been there - halfway through a cake recipe when you realize the self-raising flour tin is empty. Before you panic and abandon those scones, let me share a secret every professional baker knows: self-raising flour is just plain flour with a little chemical magic mixed in. With this guide, you'll never need to make a special grocery run again.

Unit definitions

What is plain flour (PF)?

Description: The blank canvas of baking, plain flour is wheat flour without added leavening agents.
Symbol: PF (common in UK/AU), AP flour (US)
Common uses: Bread, pastries, thickening sauces
Definition: Milled from hard wheat varieties, typically containing 9-12% protein

What is self-raising flour (SRF)?

Description: Pre mixed flour containing raising agents for convenience
Symbol: SRF (UK/AU), sometimes 'self-rising' in US
Common uses: Cakes, pancakes, quick breads
Definition: Plain flour + baking powder (4-5% by weight) + sometimes salt

Conversion formula

The golden ratio:
5g baking powder per 100g plain flour
(or 1 tsp per 100g if using volume measures)

Equation:
Self-raising flour = Plain flour + (Plain flour × 0.05)

But here's the catch - this only works if your recipe doesn't already include baking powder. Always check the original ingredients list first.

Example calculations

1. Converting 200g plain flour
   200g PF + (200 × 0.05) = 200g + 10g baking powder
   = 210g SRF equivalent
2. Reducing 300g SRF to PF
   300g SRF = 300 ÷ 1.05 ≈ 285.7g PF
   (Subtract 14.3g baking powder if needed)

Conversion tables

Plain flour to self-raising flour equivalents

Self-raising flour to plain flour reduction

Historical background

The invention of self raising flour dates back to 1845, when English baker Henry Jones patented the first commercial version. His motivation? Creating a shelf-stable flour mixture for long sea voyages - particularly for the British Navy's hardtack biscuits. Interestingly, Jones initially added salt as a preservative along with the baking powder, which is why some older recipes using SRF require less added salt.

During World War II, self raising flour became crucial for home bakers dealing with rationing. Governments promoted it as a way to stretch limited butter and egg supplies, since the built-in leavening allowed for lighter baked goods with fewer ingredients.

Interesting facts

1. Temperature matters - The acid in baking powder reacts faster in warm kitchens. For best results, mix your converted flour just before using.
2. Regional variations - Some US brands include salt (about 1/4 tsp per cup), while Australian versions often don't. Always check labels if adapting international recipes.
3. The 'double acting' difference - Most modern baking powders release gas twice: once when wet, once when heated. This gives you more flexibility in timing compared to 19th-century single-acting versions.
4. Altitude adjustments - At high elevations (above 3,000 ft), reduce baking powder by 1/8 tsp per 100g flour to prevent over-rising and collapse.
5. The gluten factor - Protein content affects rise. For airy cakes, use low-protein plain flour (9-10%). Bread flour (12-14%) makes SRF better suited for crumpets or pizza bases.

FAQ