One cup of baking soda weighs 288 g, spooned and levelled, according to King Arthur Baking. Baking soda — sodium bicarbonate — is a fine white powder that looks like baking powder but behaves very differently: it is a base, not a complete leavening system, and it needs an acid to work. The cup weight of 288 g is the same as table salt, because both are fine, dense powders that pack tightly. The figure matters for cakes, cookies and quick breads, where baking soda is measured by the teaspoon and the weight decides the rise. All weights on this page are approximate; baking soda absorbs moisture from the air, so verify with a scale when precision matters, and always use fresh soda.
Baking Soda: weight and measurement table
The table below gives the weight of baking soda in every measure you will use, from a teaspoon up to 2 cups, all derived from the King Arthur Baking figure of 288 g per cup, spooned and levelled. Every figure is approximate — spooned and levelled is a technique, not a machine setting — so when the recipe matters, weigh the ingredient on a kitchen scale instead.
| Amount | Weight (approx.) |
| --- | --- |
| 1 teaspoon | 6 g |
| 1 tablespoon | 18 g |
| 1/4 cup (4 tbsp) | 72 g |
| 1/3 cup | 96 g |
| 1/2 cup (8 tbsp) | 144 g |
| 3/4 cup (12 tbsp) | 216 g |
| 1 cup (16 tbsp) | 288 g |
| 2 cups | 576 g |
| 100 g | 0.3 cups |
There are 3 teaspoons in a tablespoon and 16 tablespoons in a cup, so you can move between any of these measures by multiplying or dividing. If a recipe calls for 100 g and you only have measuring cups, that is about 0.3 cups. Keep the cups to grams converter open while you cook and you will never need to do the arithmetic in your head.
What is Baking Soda?
Baking soda is sodium bicarbonate; it needs an acid to activate. It is a base, with a pH of about 8, and when it meets an acid — lemon juice, vinegar, buttermilk, yogurt, honey, cocoa — it reacts to release carbon dioxide, which lifts the batter. Without an acid, baking soda does almost nothing, and the unreacted soda leaves a soapy, metallic taste. It is used for leavening cakes, cookies and quick breads with acidic ingredients, and it is also used for cleaning, deodorising and softening vegetables. It should be stored in an airtight container in a cool, dry place and used within 6 months of opening, because it absorbs moisture and loses strength. Test old baking soda by dropping half a teaspoon into vinegar: vigorous fizzing means it still works.
How to measure Baking Soda correctly
Baking Soda is measured spooned and levelled, and the method matters more than most cooks realise. For dry ingredients, spoon the ingredient into the measure with a smaller spoon, letting it fall loosely, then sweep a knife across the top to level it — never dip the measuring cup into the bag, because dipping compresses the ingredient and adds up to 20 percent. For liquids, pour into a liquid measuring jug and read the level at eye height, or weigh directly into the bowl, which is the most accurate method of all. The King Arthur Baking figure used on this page is 288 g per cup, and it is the figure the site's converters use, so the numbers here and the numbers in the tool always agree. Confidence in this figure is high.
Worked examples
A chocolate cake with buttermilk
A chocolate cake uses 1.5 teaspoons of baking soda — about 7 g — with 1 cup of buttermilk and 3/4 cup of cocoa powder. The weight matters because the soda and the acid must balance: 7 g of soda against 245 g of buttermilk and 63 g of acidic cocoa gives a complete reaction, with no soda left over to taste soapy. Weighing the soda keeps the balance exact — a teaspoon too much and the cake tastes metallic, a teaspoon too little and it stays flat. The soda is sifted with the flour, which distributes it evenly, and the batter is baked immediately, because the reaction starts the moment the soda meets the buttermilk.
A batch of cookies that spread
A cookie recipe uses 1 teaspoon of baking soda — about 4.8 g — with brown sugar and butter. The weight is useful because baking soda affects spread: it raises the dough's pH, which weakens the gluten and lets the cookies spread more, giving a thin, chewy cookie with crisp edges. Weighing 4.8 g keeps the spread consistent — a teaspoon too much and the cookies spread into a single flat sheet, a teaspoon too little and they stay thick and cakey. The cookies are baked for 12 minutes, until the edges are set and the centres are still soft, and they firm up as they cool.
A soda bread for a weekend
A soda bread uses 1 teaspoon of baking soda — about 4.8 g — with 2 cups of flour and 1 cup of buttermilk. The weight matters because soda bread is the simplest leavened bread: no yeast, no waiting, just soda and acid. The soda must be fresh and the buttermilk must be acidic, or the bread will not rise. Weighing 4.8 g of soda against 245 g of buttermilk gives a balanced reaction, and the dough is mixed briefly — overmixing develops gluten and makes the bread tough — shaped into a round, scored with a cross, and baked for 45 minutes until the crust is deep brown and the loaf sounds hollow.
Acid partners and the soapy risk
Baking soda's rule is simple: it needs an acid, and the acid must match the amount of soda. The acids that work are the ones already in the kitchen — buttermilk, yogurt, sour cream, lemon juice, vinegar, honey, molasses, natural cocoa powder, brown sugar. Each of them reacts with baking soda to release carbon dioxide, and the reaction starts the moment they meet, which is why a batter made with baking soda must go into the oven quickly. The risk is unreacted soda: if there is more soda than acid, the leftover soda tastes soapy and metallic, and it turns the crumb yellow. The standard ratio is about 1/4 teaspoon of baking soda per cup of acidic ingredient, though the exact balance depends on the acid's strength. The practical rules are to use fresh soda, to measure it by weight — 4.8 g per teaspoon — to sift it with the flour so it distributes evenly, and to bake immediately. And never confuse baking soda with baking powder: baking powder is a complete leavening system that contains its own acid, while baking soda needs one from the recipe. A tablespoon of baking soda in place of baking powder is a four-fold overdose that will taste terrible.
What to use instead
If you run out of baking soda, these are the tested substitutes from our substitution data, with the ratio and the case where each one does not work. Use the ratio by weight where it is given, and check the warning before you commit the batter.
- Baking soda to Baking powder: 3 tsp baking powder per 1 tsp baking soda (omit the salt). Do not swap leavening in a recipe without acid — baking soda alone will taste soapy and will not rise.
The golden rule for any substitution is to match the job, not just the ingredient: a substitute that works in a sauce may fail in a cake, because the two recipes ask different things of the ingredient. When in doubt, use a recipe written for the substitute rather than adapting one written for the original.
Storage
Airtight container, cool and dry, up to 6 months once opened. That is the headline, but the details matter. Store baking soda in an airtight container, away from heat, light and strong smells — dry ingredients absorb odours readily, and a bag of flour stored next to the spices will taste of them within a week. Label the container with the date you opened it, so you know how long it has been there, and check it before you bake: if it smells off, tastes bitter, or shows any sign of moisture or insects, discard it. Buying in smaller quantities and using it promptly is better than buying in bulk and storing it for a year, because every ingredient loses flavour with time, even the ones that never truly go bad.
Frequently asked questions
How many grams is 1 cup of baking soda?
One cup of baking soda weighs 288 g, spooned and levelled, according to King Arthur Baking. One tablespoon weighs 18 g and one teaspoon weighs 4.8 g. In practice you will never use a cup — baking soda is measured by the teaspoon.
How many teaspoons of baking soda are in 100 g?
There are about 21 teaspoons in 100 g of baking soda (100 divided by 4.8 is 20.8). A standard 500 g box holds about 104 teaspoons, which is far more than most bakers use in a year.
Can I use baking powder instead of baking soda?
Yes, but use three times as much: 3 teaspoons of baking powder per teaspoon of baking soda, and omit the salt from the recipe. Baking powder contains its own acid, so it works without an acidic ingredient. The result will be slightly different, but it works in most recipes.
Why does my cake taste soapy?
Usually too much baking soda, or baking soda without enough acid to react with it. The unreacted soda leaves a soapy, metallic taste and turns the crumb yellow. Weigh the soda instead of spooning it, and make sure the recipe has an acidic ingredient — buttermilk, lemon juice, vinegar, yogurt or natural cocoa.
Does baking soda go bad?
Yes — baking soda loses strength with moisture and age, typically within 6 months of opening. Test it by dropping 1/2 teaspoon into vinegar: vigorous fizzing means it is still active. Store it in an airtight container in a cool, dry place.
Related pages
If you cook with this ingredient regularly, these pages will help: the cups to grams converter for any amount, the ingredient density lookup for the full table of 120 ingredients, the Baking Soda cups to grams page for cup conversions, the Baking Soda grams to cups page for working backwards from grams, and the Baking Soda tablespoons to grams page for spoon measures. You may also want Baking Powder, Salt.