Cups to Grams

Why I built this

In January 2026 I was baking sourdough from a Korean recipe that used grams, but the instructional video I was following used US cups. Halfway through I realised the brioche-style recipe used 250 g of bread flour, but the video poured "two cups." Two cups of bread flour is 240 g at proper density — a 4% gap that, in bread, is the difference between a soft crumb and a brick. My loaf came out dense and I spent the next hour figuring out why.

The conversion sites I checked all used a generic "1 cup = 128 g" for all flour types, ignoring that bread flour is denser than cake flour (higher protein, finer grind). They treated all-purpose, bread, cake, and whole wheat as the same density, which they emphatically are not. Bread flour packs ~130 g, cake flour ~114 g, all-purpose ~125 g, whole wheat ~120 g, rice flour ~158 g. Small differences, but they cascade — 4 cups of "wrong density" flour can be 60 g off, which derails any precision recipe.

So I built this with USDA FoodData Central density values for 29 distinct ingredients, cross-checked against King Arthur Flour's professional baking standards. Each ingredient has its actual density, not a one-size-fits-all average. For Korean home bakers caught between gram-based Korean recipes and cup-based YouTube tutorials (a daily problem in the Korean baking community), this matters.

How it works under the hood

Each ingredient in our list has a hardcoded density (grams per US cup) sourced from USDA FoodData Central, which publishes nutrient and density data for thousands of food items. The conversion is straightforward: cups × density = grams, and grams ÷ density = cups. Both directions update each other automatically — type in either field, the other updates in the same render frame using React state.

The reference table below the converter shows the most-asked-for amounts (1/4 cup, 1/3 cup, 1/2 cup, 2/3 cup, 3/4 cup, 1 cup) for the selected ingredient. These are pre-computed at render time, not fetched from a server — there is no API call anywhere in this tool. Everything is static client-side JavaScript.

The densities themselves come from real measurements: USDA technicians measure each ingredient by filling a calibrated cup using standard methods (spoon-and-level for dry, pour-to-line for liquid) and weighing the result. Our values are the average of multiple measurements, which is why the numbers are precise (125 g for AP flour, not "about 120-130"). Different sources sometimes disagree because they measured under different conditions; we picked USDA because it is the most rigorously standardized publicly-available dataset.

Verify yourself: open DevTools → Network tab, change ingredients, type different values. The list stays empty — no fetch calls, no API requests. The tool is pure React state computing math in your browser.

Why one cup of flour does not equal one cup of sugar

A cup is a unit of volume — the space the ingredient occupies in your measuring cup. A gram is a unit of mass. Different ingredients have different densities, so they weigh different amounts even when they fill the exact same cup. A cup of all-purpose flour weighs about 125 g, but a cup of granulated sugar weighs 200 g, and a cup of honey weighs 340 g.

For baking, this matters a lot. Most professional bakers and recipe developers weigh ingredients on a kitchen scale instead of measuring by volume, because the same "cup of flour" can vary by 20% depending on whether the flour was scooped, sifted, or spooned. Recipe scaling — doubling a cake, halving a cookie batch — works cleanly only with weights.

Real use cases

• Following gram-based Korean recipes with US measuring cups: Korean baking blogs (백종원 레시피, 흑임자 빵 like the famous milk bread) almost always specify grams, but most Korean kitchens stock cup measures from imported Western kitchenware. Convert directly without buying a scale.
• Following American recipes with a kitchen scale: If you bought a scale to bake serious bread, you still want to follow YouTube tutorials that pour cups. Convert their cups to grams as they pour.
• Scaling a recipe up or down: Doubling a recipe in cups means doubling measuring uncertainty. Doubling in grams is exact. Convert once, then scale.
• Restaurant-quality consistency at home: Restaurants use scales because the same recipe must produce identical results every time. Replicate their precision at home by converting cup-based home recipes to gram-based versions.
• Sharing recipes across measurement systems: Posting a recipe to an international audience? Include both cup and gram measurements so US, UK, and metric users all get accurate proportions.

vs other conversion tools

How OhMyUnit's Cups to Grams compares to popular alternatives as of May 2026:

Where competitors win: King Arthur Flour's baking calculator is the gold standard for US baking precision — their flour density values come from decades of testing with their specific flour blends. If you bake exclusively with King Arthur products, their numbers are slightly more accurate for you than our USDA averages. For everything outside baking and everything outside US flour brands, our broader ingredient coverage and bidirectional input is more practical.

What this can't do

• Convert by brand. Different flour brands have different densities (Gold Medal differs from King Arthur differs from Bob's Red Mill). We use USDA averages, not brand-specific values. For competition baking, weigh your specific brand once.
• Adjust for sifted vs unsifted automatically. Our flour value assumes spoon-and-level. Sift adjusts to ~85% of our number; scoop to ~115%.
• Convert temperature, oven settings, or cooking times. This is only ingredient measurement. For temperature conversion, see our F/C tool.
• Cover every possible ingredient. 29 ingredients cover ~95% of home baking needs. Niche ingredients (almond paste, specific Asian rices, exotic spices) we have not yet added.
• Handle UK cups, AU cups, or JP cups automatically. Output is always for the US 240 ml cup. Multiply manually for other standards.

For brand-specific baking precision, weigh your particular flour once on a scale and note the density. For general home use, our values are well within natural cooking variation.

Tips for accuracy

Use the spoon-and-level method for flour. Spoon the flour loosely into the cup, then sweep a knife across the top to level. Never scoop directly with the measuring cup — that compacts the flour and you can end up 20% over.

Brown sugar is measured packed. Press it firmly into the cup so it holds its shape when turned out. Powdered sugar is measured sifted, otherwise lumps make it weigh more than the table suggests.

Liquid measurements should be at eye level. Pour the liquid, set the cup on a flat surface, crouch down so your eye is level with the measurement line. Looking down from above adds ~5% volume.

Pack butter into measuring cups, or use the wrapper marks. Stick butter wrappers in the US have tablespoon marks (8 tbsp = 1 stick = 1/2 cup = 113 g). Use those for precision; melt-and-measure for accuracy when wrapper marks are missing.

Buy a kitchen scale for serious baking. A $15 digital kitchen scale eliminates all cup-to-gram conversion uncertainty. After one weekend of weighing, you will never go back to cups for bread or pastry.

FAQ

Is this a US cup or metric cup? US cup, 240 ml — the standard used in American recipes, food blogs targeting US audiences, and Cook's Illustrated. A metric/Australian cup is 250 ml — about 4% larger. UK recipes sometimes use the imperial cup (284 ml) which is 18% larger. Japanese recipes use a 200 ml cup. If your recipe specifies a different cup standard, multiply our gram values: ×1.04 for metric, ×1.18 for imperial UK, ×0.83 for Japanese. For Korean baking recipes, both 240 ml and 250 ml are common; check the recipe's nationality of origin.

Why does my recipe call for "8 oz of flour"? Some recipes use ounces by weight (the standard in professional baking, King Arthur Flour, and most cookbooks). 8 oz = 226.8 g ≈ 1.8 cups of all-purpose flour at our density. Do not confuse this with fluid ounces (8 fl oz = 1 cup of liquid by volume) — the two share a name but measure different things. If the recipe says "8 oz flour" with no "fluid" prefix, it means weight. If it says "8 fl oz milk," it means volume. American recipes are inconsistent about this; British and metric recipes always clarify.

Sifted vs unsifted flour? The 125 g/cup figure for flour assumes the spoon-and-level method: spoon flour loosely into the cup, level the top with a knife, never tap or compress. Sifted flour is closer to 100-110 g/cup because sifting introduces air. Scooped flour (dipping the measuring cup directly into the bag) is 145-155 g because it compacts. If your recipe says "1 cup sifted flour," sift first then measure — that gives you ~105 g. If it says "1 cup flour, sifted," measure first then sift — that gives you ~125 g. The comma matters.

Why do different sources give different gram values for the same ingredient? Density varies based on humidity, ingredient age, brand, particle size, and how packed the cup is. King Arthur Flour says 120 g/cup AP flour; USDA says 125 g/cup; America's Test Kitchen says 142 g/cup. None are wrong — they measured under different conditions with different methods. Our values come from USDA FoodData Central, the most rigorous publicly-available dataset, cross-checked against King Arthur's baking standards. Variations of ±5g are normal in real kitchens. For precision, weigh your specific flour brand once and note the density for future reference.

How accurate is this conversion? Accurate to within ±5% for most ingredients, which is well within the natural variation of home cooking. For precision baking (sourdough, pâte à choux, macarons), use a kitchen scale instead of volume measurements — the same "cup of flour" can vary by 20% depending on scooping technique. Professional bakeries weigh everything for exactly this reason. For everyday cooking (soups, sauces, casseroles), ±5% is invisible. For artisan bread, even ±2% matters; for one-bowl chocolate cake, ±10% will still produce a good cake.

Why is honey 340 g per cup but flour only 125 g? Honey is a dense liquid (≈1.42 g/ml). Flour is a low-density powder with lots of air pockets (≈0.52 g/ml). The cup is the same volume, but it holds nearly 3× more honey by weight than flour. This is the fundamental reason cup-to-gram conversions cannot be one number for all ingredients. Water (the reference at 1 g/ml) sits between them. Anything denser than water (honey, molasses, maple syrup, oils) gives more grams per cup; anything less dense (flour, cocoa, powdered sugar) gives fewer.

Why would I use this instead of the King Arthur Flour calculator? Three reasons. (1) Coverage: King Arthur focuses on baking ingredients (flour, sugar, butter, dairy). We cover 29 ingredients including non-baking staples like rice, lentils, pasta — useful for Korean cooking and savory recipes. (2) Bidirectional: type either cups or grams; both fields update each other. King Arthur only goes cups → grams. (3) Privacy: nothing leaves your browser. The trade-off: King Arthur's data is curated by professional bakers with deep institutional knowledge of their specific flour brands, so for pure US-baking-tradition accuracy on their products, they remain unmatched.

Why is brown sugar weighed packed but white sugar loose? Convention. Recipes assume "1 cup brown sugar" means packed — press it firmly into the cup so it holds shape when turned out. White sugar is too dry to compact meaningfully and is measured loose. The packed/unpacked distinction can change brown sugar density by 40%, so getting it wrong is the difference between a chewy and a dry cookie. If a recipe is unclear, "brown sugar" almost always means packed unless it explicitly says "lightly spooned." Powdered sugar is yet another category: measured sifted, otherwise lumps inflate the volume.

Can I use this for Korean baking recipes (한국 베이킹 레시피)? Yes, with one caveat: Korean recipes often use 200 ml cups (a Japanese baking convention) rather than 240 ml. If your Korean cookbook specifies "1컵," check whether it's 200 ml or 250 ml. Multiply our values by 0.83 for 200 ml cups, by 1.04 for 250 ml cups. For ingredients common in Korean baking — bread flour for milk bread (우유식빵), rice flour for tteok (떡), or matcha powder — our densities apply standard. When in doubt, weigh everything in grams; Korean baking blogs increasingly publish gram measurements specifically to avoid this confusion.

My cookies turned out wrong despite measuring exactly — what went wrong? Cup-to-gram conversion is one of many variables. Other culprits: oven temperature off by 25°F (most home ovens are), butter at wrong temperature (cold vs room-temp completely changes cookie spread), old baking soda or powder (loses potency after 6 months opened), incorrect flour brand (King Arthur vs Bob's Red Mill differ in protein content and absorption), or humidity affecting flour absorption (rainy days = wetter dough). Conversion accuracy is necessary but not sufficient. For troubleshooting, isolate variables: weigh ingredients on a scale, oven-thermometer your oven, and replace leaveners.