One cup of molasses weighs 340 grams when poured, according to King Arthur Baking. That makes molasses one of the heaviest common baking ingredients per cup — heavier than honey at 336 grams, far heavier than granulated sugar at 198 grams, and more than twice as heavy as a cup of brown sugar is light by comparison in handling terms. A single tablespoon of molasses weighs about 21 grams, and a teaspoon weighs about 7 grams. These are approximate figures, because molasses thickness varies with temperature — cold molasses pours slowly and traps air, warm molasses pours freely — but 340 grams per cup is the reliable reference value, and you should verify with a kitchen scale whenever the amount matters.

Molasses is the dark, thick syrup left behind when sugar cane or sugar beet juice is boiled down to extract sugar. It carries a deep, bittersweet, almost smoky flavour that defines gingerbread, baked beans, barbecue sauce, rye bread and old-fashioned spice cakes. It is also a sticky, stubborn ingredient to measure: it clings to cups and spoons, it pours in a slow ribbon, and it is very easy to end up with 20 grams more than you meant because the last of it kept dribbling in after you thought you had stopped. Weighing molasses instead of measuring it by volume solves that problem completely, and it is the single best habit you can adopt if you bake with molasses regularly.

How much does molasses weigh?

The table below gives the weight of molasses for the amounts you are most likely to meet, from a single teaspoon up to four cups. All figures come from the King Arthur Baking value of 340 grams per cup, poured. Because molasses is a liquid, the weight scales exactly with volume — but only if the cup is truly full, with no air gaps and no syrup left clinging to the sides of the measure.

Amount Weight (grams) Weight (ounces)
1 teaspoon 7 g 0.25 oz
1 tablespoon 21 g 0.75 oz
1/4 cup 85 g 3.00 oz
1/3 cup 113 g 4.00 oz
1/2 cup 170 g 6.00 oz
2/3 cup 227 g 8.00 oz
3/4 cup 255 g 9.00 oz
1 cup 340 g 11.99 oz
1 1/2 cups 510 g 17.99 oz
2 cups 680 g 23.99 oz
3 cups 1,020 g 35.98 oz
4 cups 1,360 g 47.97 oz

A useful comparison: one cup of molasses weighs nearly three times as much as one cup of all-purpose flour (120 grams) and more than one and a half times as much as one cup of water (237 grams). That density is why a gingerbread recipe that calls for a cup of molasses is adding a serious amount of weight and moisture to the batter — 340 grams of liquid sugar — and why the liquid balance of the recipe has to account for it. If you ever wondered why gingerbread dough is so soft and sticky, the answer is sitting in this table.

For everyday baking, the tablespoon and quarter-cup rows are the ones that matter. Most gingerbread and spice cake recipes call for 1/2 to 1 cup of molasses, which is 170 to 340 grams. Most barbecue sauces call for 2 to 4 tablespoons, which is 42 to 85 grams. Weighing these amounts takes seconds: put the bowl on the scale, tare it, and pour until the number is right. No scraping, no sticky measuring cup, no washing up a jug coated in syrup.

Worked examples

Example 1: A gingerbread house that holds its shape

A gingerbread recipe for a house calls for 1 cup of molasses — 340 grams. You are making the dough on a cold winter morning and the molasses is thick and slow from sitting in a cool pantry. You measure it by volume in a cup, but the cold syrup leaves a thick coating inside the measuring cup, so only about 310 grams actually makes it into the bowl. The dough comes out dry and crumbly, and the walls crack when you try to assemble the house. The fix is to weigh the molasses: put the mixing bowl on the scale and pour 340 grams straight in. If the molasses is cold, warm the jar for a few minutes in a bowl of warm water first so it pours cleanly. The dough will have the right moisture, and the house will stand.

Example 2: Scaling a barbecue sauce for a party

Your barbecue sauce recipe makes 2 cups and calls for 1/4 cup of molasses — 85 grams. You are scaling it up five times for a summer party, so you need 425 grams, or 1 1/4 cups. Measuring 1 1/4 cups of molasses by volume means five sticky pours and five scrapings. Weighing means putting the pot on the scale, taring it, and pouring until it reads 425 grams. It also means the sauce tastes the same as the small batch, because the ratio is exact. With a sweetener as assertive as molasses, a 20-gram error changes the flavour noticeably; weighing removes that risk.

Example 3: Converting a baked beans recipe to grams

A slow-cooker baked beans recipe written in American cups calls for 1/3 cup of molasses, and you are converting the whole recipe to grams for a friend who bakes by weight. One third of a cup is 113 grams. While you are at it, the recipe's 2 tablespoons of molasses in the glaze is 42 grams. Note the rounding: a third of 340 is 113.3, so 113 grams is right, and the 0.3-gram difference is meaningless in a pot of beans. What is not meaningless is the difference between measuring 1/3 cup of cold molasses in a dry measure — where a good 10 grams can stay behind on the cup — and weighing it.

Method and source

The figure of 340 grams per cup comes from King Arthur Baking's ingredient weight chart, measured poured — molasses is a liquid, so it is poured into a measure rather than spooned or packed. King Arthur lists the value with high confidence. There is no serious dispute about it, though different types of molasses vary slightly: light molasses is a little thinner and lighter, blackstrap molasses — the darkest, most bitter grade — is slightly denser. The 340-gram figure is for the standard unsulphured molasses most recipes mean when they simply say "molasses."

Temperature is the one variable that matters. Molasses at fridge temperature is almost solid and traps air bubbles as it pours, so a cup measured cold can weigh less than 340 grams even when it looks full. Molasses warmed to room temperature pours cleanly and gives a true measure. If you are weighing it, temperature does not matter to the weight — 340 grams is 340 grams whether it is cold or warm — which is another reason weighing is better. Warm it only to make it pourable.

One distinction worth making: molasses is not the same as treacle, though the two are often confused. Golden syrup, the pale treacle sold in British shops, weighs about 312 grams per cup — noticeably lighter than molasses. Black treacle is close to molasses in weight and flavour and can usually be swapped cup for cup, but golden syrup cannot: it is lighter, sweeter and far less bitter, and a recipe that expects molasses will taste wrong with golden syrup in its place.

Practical guidance

The single most useful trick for handling molasses is to oil the measure. If you must measure by volume, spray the cup or spoon lightly with cooking oil first, or brush it with a drop of vegetable oil: the molasses will slide out cleanly instead of clinging. Better still, weigh it — the bowl goes on the scale, the molasses goes straight in, and there is nothing to scrape or wash except the bowl you were already using.

Molasses is hygroscopic, meaning it attracts moisture from the air, and it is also acidic, with a pH around 5. That acidity is useful in baking: it activates baking soda, which is why gingerbread recipes pair molasses with baking soda rather than baking powder. It also means that swapping molasses for another sweetener changes the leavening — if you replace molasses with honey, which is less acidic, a recipe leavened with baking soda may not rise properly. If you must substitute, use dark brown sugar dissolved in a little water (1 cup of brown sugar plus 2 tablespoons of water replaces 1 cup of molasses approximately), or use an equal amount of black treacle, and accept that the flavour will shift.

The most common mistakes are measuring cold molasses by volume and losing 10 to 20 grams to the sides of the cup; substituting honey or maple syrup cup-for-cup, which changes both the flavour and the acidity of the recipe; and storing molasses badly. Storage is simple: an airtight jar in a cool, dark place keeps for up to a year. It will not go mouldy — the sugar concentration is too high — but it can crystallise in cold storage. If crystals form, stand the jar in warm water and stir until they dissolve. Do not refrigerate molasses; the cold makes it thick and hard to pour, and the crystallisation happens faster.

Frequently asked questions

How many grams is 1 cup of molasses?

One cup of molasses weighs 340 grams, poured, according to King Arthur Baking. That is the figure to use for recipe conversion and scaling. Half a cup is 170 grams, a quarter cup is 85 grams, and a tablespoon is about 21 grams. All of these are approximate — molasses varies slightly by grade and temperature — so verify with a kitchen scale when the amount matters.

How many grams is 1 tablespoon of molasses?

One tablespoon of molasses weighs about 21 grams. Two tablespoons is 42 grams, and three tablespoons (a quarter cup) is 85 grams. If you are adding molasses to a sauce or glaze by the spoonful, weighing the spoonfuls is far more accurate than pouring from the jar, because molasses keeps dribbling after you stop pouring.

Is molasses heavier than honey?

Yes, very slightly. One cup of molasses weighs 340 grams, while one cup of honey weighs 336 grams. The difference is only 4 grams per cup — about 1 percent — so for practical purposes they weigh the same. What differs is the flavour and the acidity: molasses is bitter, dark and acidic, while honey is sweet, floral and only mildly acidic, so they are not interchangeable in recipes even though their weights are nearly identical.

Can I substitute honey for molasses?

You can, but the result will be different. Use the same amount by volume — 1 cup of honey for 1 cup of molasses — and expect a lighter colour, a sweeter and less complex flavour, and less acidity. Because molasses activates baking soda and honey does so only weakly, a gingerbread leavened with baking soda may rise less with honey. A better substitute is dark brown sugar dissolved in water, or black treacle, which is much closer in flavour.

What is the difference between light molasses and blackstrap molasses?

Light molasses is the syrup from the first boiling of sugar cane juice; it is sweet, mild and amber-coloured. Blackstrap is the syrup from the third boiling; it is very dark, bitter, and much lower in sugar, but higher in minerals like iron and calcium. Most recipes that say "molasses" mean light or dark (second-boiling) molasses. Do not use blackstrap in a recipe that calls for regular molasses unless you want a much more bitter result — and do not use it in the same amount, because its lower sugar content changes the sweetness.

How should I store molasses?

Keep molasses in an airtight jar in a cool, dark cupboard for up to a year. Do not refrigerate it — the cold makes it thick, hard to pour and prone to crystallising. If crystals form, stand the sealed jar in a bowl of warm water and stir until the crystals dissolve. Molasses does not go mouldy under normal storage because its sugar concentration is too high for mould to grow.

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