Baking soda vs baking powder: the difference and how to swap them
Baking soda and baking powder look almost identical in the tub, and both make a batter rise. They are still not the same thing, and you cannot swap one for the other in the same amount. The wrong choice or the wrong quantity shows quickly: the cake stays flat, the pancakes taste of soap or the top of a muffin turns an odd dark colour.
In this guide we explain the difference between baking soda and baking powder, when to use each, how to replace one with the other and how to test whether the forgotten tub at the back of the cupboard still works.
The short answer: what is the difference?
Baking soda is pure sodium bicarbonate. It is an alkaline ingredient that only releases carbon dioxide when it meets an acidic ingredient and liquid. Baking powder is a ready-made mix of baking soda, an acidic salt and a little starch to absorb moisture. In other words, baking powder carries its own acid and baking soda does not.
That gives a practical rule: use baking soda in batters that already contain something acidic, and baking powder in batters that do not. Baking soda is also much stronger, so you only need a small amount. According to international baking guides, baking soda has roughly three to four times the raising power of baking powder.
When to use baking soda
Baking soda suits batters with a cultured dairy product or another acidic ingredient, such as buttermilk, yoghurt, sour cream, quark, lemon juice, honey, syrup or cocoa. The soda and the acid react as soon as the batter gets wet, so a batter raised with baking soda should be baked quickly. If it sits for a long time, the bubbles escape before it reaches the oven.
Baking soda also affects flavour and colour. It neutralises sourness and helps baked goods brown, which is why it is used in gingerbread and dark cakes. Too much of it, however, leaves a bitter, soapy or metallic aftertaste and can turn the crumb yellowish or dark.
When to use baking powder
Baking powder is the easy choice when there is nothing acidic in the batter, for example in plain sponge cakes, muffins and quick breads such as banana bread. Most shop-bought baking powders work in two stages: some of the gas is released when the batter gets wet and most of it only in the heat of the oven. That is why a baking powder batter tolerates a short wait better than a baking soda batter.
The same logic applies to savoury batters. When you make our crispy courgette fritters with Balkan cheese or a Japanese okonomiyaki cabbage pancake with bacon, follow the recipe closely: too much raising agent makes the batter fluffy but fragile, and it falls apart easily in the pan. Some recipes use both baking soda and baking powder. In that case the soda neutralises the acidic ingredient and the baking powder takes care of the rest of the rise.
Baking soda and baking powder: quick checklist
Baking soda needs an acidic ingredient in the batter, such as yoghurt, buttermilk or lemon juice. Baking powder already contains its own acid.
You need far less baking soda than baking powder, so never swap them one for one.
One teaspoon of baking soda can be replaced with roughly 2 to 3 teaspoons of baking powder.
A batter raised with baking soda starts reacting as soon as it gets wet, so bake it as soon as possible.
Use a level measuring spoon: a teaspoon is 5 ml, and a heaped spoon can add up to half as much again.
Test: baking powder fizzes in hot water, baking soda fizzes when you add vinegar.
Store both tightly closed in a dry place, because moisture weakens their raising power.
Can you replace baking soda with baking powder?
Yes, and it is the easier direction. Because baking powder already contains baking soda, one teaspoon of baking soda can be replaced with roughly 2 to 3 teaspoons of baking powder. Some guides recommend double the amount, others triple. Start with less if the batter contains a lot of acidic ingredients. The result may taste slightly tangier and brown less, but the cake will rise.
The other way round is trickier. You can only replace baking powder with baking soda if the batter contains enough acid, and even then you need just a fraction: one teaspoon of baking powder corresponds to roughly a quarter teaspoon of baking soda. Without acid, baking soda leaves a bitter taste and does not raise the batter properly.
Small amounts are worth measuring precisely. A teaspoon is 5 millilitres, and a level measuring spoon gives a far more reliable result than a heaped tablespoon. Read more about kitchen measurements and conversions.
Other raising agents
Yeast and air also make things rise. Whisked eggs make a cake light without any raising agent at all, as in a classic sponge. Fresh eggs give the best foam, so also see our tips on checking egg freshness. In some older recipes you may also come across baker's ammonia, or ammonium bicarbonate. It suits thin, crisp biscuits, where the ammonia smell evaporates during baking, but not thick cakes.
How to test whether a raising agent still works
Raising agents lose strength over time and with moisture. To test baking powder, stir half a teaspoon into hot water. If it fizzes vigorously straight away, it is fine. To test baking soda, add a quarter teaspoon to a small amount of vinegar or lemon juice. Strong fizzing means it still works. If you only see a few bubbles, it is time for a new tub.
Baking soda in everyday cooking
Baking soda is useful beyond baking too. A pinch in the soaking or cooking water for dried chickpeas or beans softens them faster. A tiny amount added to frying onions speeds up browning, although it also makes them softer. In both cases a small amount is enough, because too much baking soda can be tasted.
Storage
Keep baking soda and baking powder in a tightly closed container in a dry, cool cupboard, away from the hob and dishwasher steam. Moisture starts the reaction inside the packet and weakens the raising power. Write the opening date on the packet so you remember to test it before you next bake. Once your cupboard is sorted, find inspiration in our recipes.
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