Converting cups to millilitres should be the easiest job in the kitchen — and for the volume, it is. One US cup is 236.6 ml, full stop, for every ingredient from flour to fruit. The trouble starts when a recipe also needs grams, because a cup of baking soda does not weigh the same as a cup of anything else. It weighs about 288 g, measured spooned and levelled according to King Arthur Baking, and that weight is what this page is really about. Below you will find the answer up front, a complete conversion table for every fraction of a cup, three worked examples, the method and source behind the numbers, and practical advice for measuring baking soda properly. All the figures are labelled approximate, and where it matters we will keep telling you the same thing: verify with a kitchen scale.
How much is 1 cup of baking soda in millilitres?
1 cup of baking soda is 236.6 ml and weighs about 288 g. The millilitre figure is exact, because a US cup is defined as 236.6 ml: fill any cup measure to the brim with any ingredient and you have 236.6 ml of it. The gram figure is approximate, because it depends on the density of baking soda and on how the cup was filled. The value we use, 288 g, comes from King Arthur Baking, measured spooned and levelled, and we use it with high confidence. If you are baking, scaling a recipe, or cooking for someone with a dietary restriction, weigh the baking soda on a kitchen scale and use the gram figure — it is the only measurement that does not depend on how fluffy, damp or tightly packed the ingredient happens to be today.
That distinction between exact volume and approximate weight is the single most useful thing to understand about cup conversions. Recipes written in cups assume a standard cup and a standard technique, and when either of those assumptions breaks, the recipe breaks with it. A cup of baking soda scooped straight from the bag can weigh noticeably more than a cup spooned in gently, and the difference is invisible until the finished dish tells you about it. The table below gives you both figures for every amount you are likely to need, so you can convert in either direction without doing the arithmetic yourself.
Cups to millilitres table for baking soda
| Cups | Millilitres | Grams (approx.) |
|---|---|---|
| ¼ cup | 59.2 ml | 72 g |
| ⅓ cup | 78.9 ml | 96 g |
| ½ cup | 118.3 ml | 144 g |
| ⅔ cup | 157.7 ml | 192 g |
| ¾ cup | 177.5 ml | 216 g |
| 1 cup | 236.6 ml | 288 g |
| 2 cups | 473.2 ml | 576 g |
| 3 cups | 709.8 ml | 864 g |
| 4 cups | 946.4 ml | 1152 g |
Every row in this table follows the same two rules. The millilitre column is the cup fraction multiplied by 236.6 ml, so a quarter cup is 59.2 ml, a third of a cup is 78.9 ml, half a cup is 118.3 ml, two-thirds is 157.7 ml, and three-quarters is 177.5 ml. Those numbers are exact to one decimal place and they are the same for every ingredient on this site. The gram column is the same fraction multiplied by 288 g, the weight of a full cup of baking soda, and those numbers are approximate: a quarter cup is about 72 g, half a cup about 144 g, and four cups about 1152 g. Use the millilitres when you are measuring volume, and the grams when you are measuring weight — and remember that only the grams need a scale to check.
There is one more conversion worth knowing. One US cup is 8 US fluid ounces, so 1 cup of baking soda is also 8 fl oz by volume — but fluid ounces are a volume measure, not a weight measure, and baking soda does not weigh 8 ounces. Do not confuse the two: 8 fl oz of baking soda is a volume of 236.6 ml, while the weight is about 288 g. If a recipe gives ounces and you are not sure which kind it means, check whether it is talking about a measuring jug (fluid ounces, volume) or a scale (ounces, weight). When a recipe is ambiguous, the gram figure on this page is the safer one to follow.
Worked examples
Doubling a batch of muffins
A muffin recipe that uses 1 teaspoon of baking soda per batch needs 2 teaspoons when doubled — about 24 g. Do not be tempted to add a little extra 'for safety': leaveners do not work that way, and extra baking soda makes muffins rise fast and then sink, with a bitter aftertaste. Double exactly, level every spoon, and get the tray into the oven promptly.
A bulk bake for a market stall
If you bake in bulk and a recipe calls for ¼ cup of baking soda, that is 59.2 ml and about 72 g. At this scale, weighing is not optional: a quarter-cup measured with a heaped spoon can be a third heavier than the recipe intends, and across a dozen trays that error is visible in every single bake. Spoon, level, weigh, and write the gram figure on your recipe card for next time.
A cake that needs two teaspoons
Almost no recipe uses a cup of baking soda; a typical cake uses 1–2 teaspoons. One teaspoon is about 6.0 g, so two teaspoons are about 12 g. That small number is why the cup figure matters: it is the only way to know what a teaspoon actually weighs, and with a leavener a heaped teaspoon instead of a level one can be the difference between a good rise and a collapsed centre.
How to measure 1 cup of baking soda
Baking Soda is one of the ingredients where the cup-to-gram figure is not a convenience but a safety net. Leaveners work in narrow ranges: too little and a cake stays flat, too much and it rises fast, collapses, and tastes soapy or metallic. That is why the 288 g per cup figure matters even though almost no home recipe ever uses a whole cup of baking soda. It is the anchor for every smaller amount — a teaspoon is about 6.0 g, a tablespoon about 18.0 g — and it is what lets you scale a recipe accurately instead of guessing with a spoon that may be heaped or level. Always measure baking soda with the spooned-and-levelled method described below, and never pack it down. A packed cup can hold far more than 288 g, and in a leavener that error goes straight into the crumb of the bake.
The method behind our figure is spooned and levelled, and the source is King Arthur Baking. In practice that means: take a dry measuring cup, spoon the baking soda in until it heaps above the rim, then sweep a straight edge — the back of a knife is ideal — across the top to level it. Do not scoop the cup through the ingredient, do not tap the cup on the bench to settle the contents, and do not press the ingredient down. Each of those shortcuts packs more into the cup and makes the weight higher than the 288 g in the table, sometimes by a surprising amount. For a liquid or a pourable ingredient the method is simpler: pour into a liquid measuring jug, set it on a flat surface, and read the level at eye height.
If you do not have a scale, the spooned-and-levelled cup is the best you can do, and for most everyday cooking it is good enough. But if the recipe is a bake, a preserve, or anything where the ratio of ingredients does the structural work, borrow or buy a scale: even a basic digital scale is more accurate than the best cup technique, and it is faster once you are used to it. Put the bowl on the scale, press tare, and add baking soda until the display reads the grams you need. That is the whole technique, and it removes the single biggest source of variation in cup-based recipes.
Why precision matters more here than anywhere else
Baking Soda is used for leavening cakes, cookies and quick breads with acidic ingredients. Sodium bicarbonate; needs an acid to activate.
Keep it dry and check the date
Airtight container, cool and dry, up to 6 months once opened. Moisture is the enemy: a damp leavener starts reacting in the jar instead of in the oven, and once it has reacted it cannot be un-reacted. Store baking soda in a truly airtight container, and test it before an important bake — a spoonful in hot water should fizz vigorously for baking soda, and a spoonful in hot water should bubble for baking powder. If it does not, replace it; no conversion table can save a dead leavener.
Measure last, bake immediately
Once baking soda meets liquid, the clock starts. Measure it last, add it to the dry ingredients, and get the batter into the oven promptly. A batter that sits on the bench for twenty minutes has already spent much of its lift, and the cake will be dense no matter how accurately you measured.
Common mistakes with cups and millilitres
The most common mistake is treating the millilitre figure and the gram figure as interchangeable. They are not: 236.6 ml is a volume and 288 g is a weight, and the only ingredient for which they are equal is water, where 1 ml weighs 1 g. For baking soda, 236.6 ml weighs about 288 g, and if you weigh out 236.6 g of baking soda instead of measuring 236.6 ml, you will have the wrong amount — too much if 288 is greater than 236.6, too little if it is less. Always check whether the recipe wants a volume or a weight, and use the matching column of the table.
The second most common mistake is using the wrong cup. A US cup is 236.6 ml, a metric cup is 250 ml, and a UK cup in older recipes can mean something else again. If your measuring cup came with a set that does not say which standard it follows, check it against a measuring jug: fill the cup with water and pour it into the jug. If it reads 236.6 ml, it is a US cup; if it reads 250 ml, it is a metric cup. Once you know, write it on the cup with a permanent marker so you never have to guess again.
The third mistake is measuring over the mixing bowl. It feels efficient, but a spill goes straight into the batter and cannot be taken back, and a cup read from above always looks fuller than it is. Measure over the sink or a plate, level the cup, and then tip it into the bowl. It takes five seconds longer and it prevents the kind of error that ruins a bake.
Frequently asked questions
How many millilitres is 1 cup of baking soda?
1 cup of baking soda is 236.6 ml. That figure is fixed: a US cup is defined as 236.6 ml, so it is the same for every ingredient. What changes from one ingredient to another is the weight, and 1 cup of baking soda weighs about 288 g. The volume never changes; the weight always depends on the ingredient.
How many grams is 1 cup of baking soda?
1 cup of baking soda weighs about 288 g, measured spooned and levelled according to King Arthur Baking. The word "about" matters: the exact weight of a cup depends on how the ingredient is handled, how finely it is ground or cut, and how much moisture it holds. For baking and for any recipe where the amount is critical, weigh the ingredient on a kitchen scale rather than trusting the cup.
Is 1 cup of baking soda the same as 250 ml?
No. A US cup is 236.6 ml, while a metric cup — used in Australia and in many metric recipes — is 250 ml. The difference is 13.4 ml per cup, which is about 5.7%. If your recipe was written with metric cups and you measure with a US cup, you will be short on every cup; if it was written with US cups and you use a metric cup, you will be over. Check which cup your recipe means, and when in doubt use the gram figure, 288 g, which does not depend on the cup at all.
How many tablespoons of baking soda are in a cup?
There are 16 tablespoons in 1 cup, so 1 cup of baking soda is 16 tablespoons, weighing about 288 g in total. One tablespoon is about 18.0 g and one teaspoon is about 6.0 g. These spoon figures are worked back from the cup weight, so they carry the same approximation — they are useful for small amounts, but for a full cup the scale is still the more accurate tool.
Can I use more baking soda to make a cake rise higher?
No. Sodium bicarbonate; needs an acid to activate. Leaveners work in a narrow range, and adding extra does not add extra lift — it makes the batter rise too fast, collapse, and taste bitter or soapy. Use exactly the amount the recipe specifies, measured level, and make sure the leavener is fresh. If a cake is not rising, the cause is usually an old leavener or an oven that is too cool, not too little leavener.
Can I use a kitchen scale instead of a cup for baking soda?
Yes, and for most recipes you should. Put your bowl on the scale, press tare to zero it, and add baking soda until the display reads the grams you need — 288 g for a full cup, 144 g for half a cup, 72 g for a quarter cup. A scale removes every variable that makes cup measuring unreliable: how firmly the ingredient was packed, how it was scooped, and how humid the day is.
Why does the weight of a cup of baking soda vary between sources?
Different sources measure differently. Some scoop the cup through the ingredient, some spoon it in, some pack it down, and some use a different variety or a different moisture level. The figure on this page, 288 g, comes from King Arthur Baking using the spooned and levelled method, which is the most repeatable way to fill a cup. If another source gives a different number, it is usually because the method was different — not because one of them is wrong.