Understanding the conversion between volume and weight is one of the most critical skills a home cook or baker can develop. When a recipe calls for 2/3 cup, the weight in grams changes drastically depending on the ingredient you are measuring. Unlike milliliters, which measure volume consistently, grams measure mass, meaning the density of the ingredient dictates the final number. For water, the baseline is approximately 158 grams, but for flour, it drops to roughly 80 grams, while packed brown sugar jumps to around 135 grams. Mastering this distinction separates guesswork from precision, ensuring your cakes rise, your breads develop structure, and your sauces thicken perfectly every single time.
Why Volume-to-Weight Conversions Matter
Professional bakers rarely rely on measuring cups. The reason is simple: volume measurements are inherently inconsistent. That said, how tightly you pack a cup of flour, whether you sift it first, or how much you shake the cup to level it off can alter the actual amount of ingredient by 20% or more. They rely on digital kitchen scales. In baking, where chemistry relies on precise ratios of flour to liquid, fat to sugar, and leaveners to acid, that margin of error is the difference between a tender crumb and a dense brick No workaround needed..
When you see 2/3 cup in a recipe, you are looking at a volume measurement equivalent to roughly 158 milliliters. That said, translating that 158 ml into grams requires knowing the specific density of the substance. This article breaks down the exact gram weights for the most common baking and cooking ingredients so you can achieve professional results with confidence.
Easier said than done, but still worth knowing Not complicated — just consistent..
The Baseline: Water and Thin Liquids
The easiest conversion to remember is for water, milk, oil, and other thin liquids with a density very close to 1 g/ml. Since 1 US cup equals 236.Even so, 588 ml, 2/3 cup equals approximately 157. 7 ml, which we round to 158 grams The details matter here..
- Water: 158 g
- Whole Milk: ~162 g (slightly denser due to fat and solids)
- Vegetable/Canola Oil: ~144 g (less dense than water)
- Heavy Cream: ~160 g
- Honey/Maple Syrup: ~225 g (significantly denser due to high sugar concentration)
Pro Tip: For oils and syrups, lightly spray your measuring cup with non-stick spray before pouring. The liquid will slide out completely, ensuring you get the full weight into your bowl That alone is useful..
Dry Goods: Flours, Sugars, and Starches
This category sees the most variation because of "aeration." A cup of flour scooped directly from the bag (the "dip and sweep" method) weighs significantly more than a cup of flour that has been fluffed, spooned into the cup, and leveled off The details matter here..
All-Purpose Flour & Bread Flour
The standard conversion used by most culinary institutions (like King Arthur Baking) assumes the "spoon and level" method Small thing, real impact. Took long enough..
- 1 Cup (spooned & leveled): ~120 g – 125 g
- 2/3 Cup: 80 g – 83 g
If you dip the cup into the bag and shake it level, you could easily get 140g–150g per cup, pushing 2/3 cup to nearly 100g. This is why weighing flour is non-negotiable for artisan bread and delicate pastries And it works..
Cake Flour & Pastry Flour
These are lower protein and often finer, resulting in a lighter weight per cup.
- 1 Cup: ~100 g – 110 g
- 2/3 Cup: 67 g – 73 g
Whole Wheat Flour
Denser and heavier due to bran and germ.
- 1 Cup: ~120 g – 128 g
- 2/3 Cup: 80 g – 85 g
Granulated White Sugar
Sugar crystals pack relatively uniformly Simple, but easy to overlook..
- 1 Cup: 200 g
- 2/3 Cup: 133 g
Brown Sugar (Light or Dark)
Recipes almost always specify "packed." This means you press it firmly into the cup until it holds the shape of the cup when turned out Not complicated — just consistent..
- 1 Cup Packed: 213 g – 220 g
- 2/3 Cup Packed: 142 g – 147 g
Powdered Sugar (Confectioners' Sugar)
Light and fluffy unless sifted.
- 1 Cup Unsifted: ~120 g
- 1 Cup Sifted: ~100 g
- 2/3 Cup Unsifted: 80 g
- 2/3 Cup Sifted: 67 g
Cocoa Powder
Like flour, cocoa compacts easily. Always spoon and level.
- 1 Cup: ~85 g – 90 g
- 2/3 Cup: 57 g – 60 g
Cornstarch / Cornflour
- 1 Cup: ~120 g
- 2/3 Cup: 80 g
Fats: Butter, Shortening, and Nut Butters
In the US, butter is conveniently sold in sticks marked with tablespoon and cup lines. 2/3 cup of butter is exactly 10 tablespoons + 2 teaspoons (or 1 stick + 2 tbsp + 2 tsp).
Butter
- 1 Cup (2 sticks): 227 g
- 2/3 Cup: 151 g
Shortening / Lard
These are 100% fat with no water content, making them slightly lighter by volume than butter And it works..
- 1 Cup: ~190 g – 205 g (varies by brand aeration)
- 2/3 Cup: 127 g – 137 g
Peanut Butter / Almond Butter / Tahini
These are dense and sticky.
- 1 Cup: ~250 g – 270 g
- 2/3 Cup: 167 g – 180 g
Measuring Hack: For sticky fats, use the water displacement method if you don't have a scale. Fill a 2-cup liquid measure with 1 cup of cold water. Add peanut butter until the water level rises to 1 2/3 cups. The peanut butter displaces the water perfectly. Drain the water, and you have your 2/3 cup.
Leaveners, Salt, and Spices
These are used in small quantities, but precision is vital for chemical reactions.
Baking Powder / Baking Soda
- 1 Teaspoon Baking Powder: ~4.6 g
- 1 Teaspoon Baking Soda: ~5 g (denser)
- 2/3 Cup (approx 32 tsp): 147 g (Powder) / 160 g (Soda) Note: You will almost never measure 2/3 cup of leavener in a home recipe, but the per-teaspoon weight is essential for scaling formulas.
Table Salt vs. Kosher Salt vs. Sea Salt
This is the most dangerous conversion trap in the kitchen Surprisingly effective..
- **Table Salt
Table Salt: Fine, uniform granules with high density.
- 1 Cup: ~273 g – 300 g
- 2/3 Cup: 182 g – 200 g
Kosher Salt
Larger, irregular flakes mean far more air between grains; weight varies significantly by brand Worth keeping that in mind. Nothing fancy..
- Diamond Crystal (1 Cup): ~112 g → 2/3 Cup: 75 g
- Morton (1 Cup): ~228 g → 2/3 Cup: 152 g Note: These two brands are not interchangeable by volume. A cup of Morton weighs roughly twice as much as a cup of Diamond Crystal.
Sea Salt / Flaky Salt
Highly variable based on crystal size and moisture content.
- 1 Cup: ~130 g – 200 g
- 2/3 Cup: 87 g – 133 g
Bottom Line
There is no universal gram weight for “2/3 cup.Plus, ” A cup of flour, sugar, butter, or salt each occupies space differently, and how you scoop, sift, pack, or level changes the result. Because of that, for baking—where chemistry depends on precise ratios—a digital scale is the only way to guarantee consistency. If you must measure by volume, spoon dry ingredients lightly into the cup and level with a straight edge; never pack unless the recipe explicitly says so (as with brown sugar). In practice, when in doubt, weigh it out. Your cakes, cookies, and breads will thank you.
