Baking Soda and Baking Powder: Grams, Teaspoons and Substitutions
A teaspoon of either is about 4.8 g, but they do completely different jobs. Here is how to measure them, substitute them and stop over-using them.
A teaspoon of either is about 4.8 g, but they do completely different jobs. Here is how to measure them, substitute them and stop over-using them.
Baking soda and baking powder look alike, measure the same by volume, and do entirely different things. Confusing them is one of the more common reasons a bake fails in a way that is hard to diagnose.
What each one actually is
Baking soda is sodium bicarbonate, a single alkaline compound. It produces carbon dioxide only when it meets an acid and moisture. On its own in a batter it does nothing except taste soapy.
Baking powder is baking soda with a powdered acid already mixed in, plus a starch to keep the two apart while dry. Add liquid and it works on its own, no acid needed from the recipe.
Most baking powder is double-acting: one burst of gas when it gets wet, a second in the oven when it heats. That second burst is why a batter can sit for a few minutes without disaster.
Measuring them
Level, always. A heaped teaspoon of baking soda can hold half as much again, and with an ingredient this powerful that is not a rounding error. Fill the spoon and sweep it flat.
Both also clump, especially in humid kitchens. Break up any lumps before measuring or you will get a pocket of raw bicarbonate in the finished bake — a bitter patch in one corner of an otherwise good cake.
How much to use
These are the ranges you will meet in home recipes, not rules:
Baking powder: about 1 to 1½ teaspoons per cup of flour (125 g).
Baking soda: about ¼ teaspoon per cup of flour, and only when the recipe has an acid.
Which acids activate baking soda
If a recipe uses baking soda, look for one of these. If none is present, the recipe probably wants baking powder.
Buttermilk, yoghurt, sour cream
Brown sugar and molasses
Substituting one for the other
Baking soda instead of baking powder: possible but fiddly. You need a quarter teaspoon of soda plus half a teaspoon of cream of tartar to replace one teaspoon of baking powder — and the mixture is single-acting, so get it into the oven promptly.
Baking powder instead of baking soda: use about three times as much. One teaspoon of baking soda becomes about three teaspoons of baking powder. Two things then change: you have added a lot more powder, which can leave a chemical aftertaste, and the recipe's acid now has nothing to neutralise it, so the batter will be more acidic and will brown less.
The honest answer is that neither substitution is good. Both boxes cost very little and last a long time. Keep both.
Testing whether they still work
Baking powder loses strength over months once opened. Baking soda lasts almost indefinitely if kept dry and sealed, but it absorbs odours — the box in the back of the fridge is doing its job and should not go into a cake.
Baking powder: stir half a teaspoon into a few tablespoons of hot water. Vigorous immediate fizzing means it is fine.
Baking soda: stir half a teaspoon into a few tablespoons of vinegar. Same test, same expectation.
What too much looks like
Too much baking soda: a soapy, metallic, faintly bitter taste. A cake that rises fast then sinks in the middle. Excessive browning, because alkalinity accelerates the Maillard reaction. A coarse, open crumb.
Too much baking powder: a bitter chemical aftertaste. A batter that overflows the tin, then collapses as the structure cannot hold the gas. Large irregular holes in the crumb.
Both failures look like the bake rose beautifully and then gave up. If that keeps happening, measure the leavener level and check the box is still active before changing anything else.
Altitude
Above roughly 1,000 metres, lower air pressure lets gas expand more, so bakes rise faster and can collapse before the structure sets. The usual adjustment is to reduce the leavener by about a quarter and add a little extra liquid.
This is a real effect with well-established guidance, but it is specific enough to your altitude that it is worth finding advice for your own elevation rather than applying a single rule.
For the measurements themselves, the grams to teaspoons converter covers both leaveners, and the teaspoons to tablespoons page has the wider table of small-quantity ingredients.
Frequently asked questions
How many grams is a teaspoon of baking powder?
About 4.8 g. Baking soda is the same by volume, at roughly 4.8 g per level teaspoon.
Can I substitute baking powder for baking soda?
Only in one direction and with adjustment. Baking powder is roughly a third as strong, so you need about three times as much — and the recipe's acid will then have nothing to react with, which changes the flavour and browning.
How much baking powder per cup of flour?
The usual range is 1 to 1½ teaspoons per cup of flour, which is about 1 to 1½ teaspoons per 125 g.
Why does my cake taste soapy or metallic?
Almost always too much baking soda, or baking soda without enough acid to neutralise it. Unreacted bicarbonate has a distinctly soapy, bitter taste.
How do I know if my baking powder is still good?
Stir half a teaspoon into a few tablespoons of hot water. It should fizz vigorously straight away. For baking soda, use vinegar instead of water.