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2.5 cups of flour is 300 g. A cup of sugar is 200 g, butter 227 g, honey 340 g — the same cup, four different weights.
A cup measures volume; baking cares about mass. A cup of flour weighs 120 g while a cup of honey weighs 340 g — and a scooped cup of flour packs 30% heavier than a spooned one. This converter uses the standard spooned-and-leveled values (the King Arthur convention) for the ingredients that matter, in grams and ounces.
Bakers use it to end the variance: 2.5 cups of flour is 300 g — but a cup of sugar is 200 g and butter 227 g, because volume lies and mass doesn't.
Because flour compresses: dipping the measuring cup into the bag packs it to 140–160 g, spooning-and-leveling gives the standard 120 g, and sifted flour drops to ~100 g — a 50% spread from the same "cup." Humidity and settling compound it. That variance is bigger than most recipe tolerances, which is why professional baking abandoned volume: 300 g of flour is 300 g every time, anywhere on earth. The cup conventions worth knowing: US cup = 236.6 mL, metric cup (Australia) = 250 mL, and old British recipes use imperial cups at 284 mL — a 20% spread before ingredient density even enters. When a recipe fails consistently, measuring technique is the first suspect, not the recipe.
The baker's core table (spooned-and-leveled, King Arthur standard): all-purpose flour 120 g, bread flour 127 g, granulated sugar 200 g, packed brown sugar 220 g, powdered sugar 120 g, butter 227 g (exactly one US half-pound block = 2 sticks = 1 cup), milk and water 240 g, oil 218 g, honey 340 g, uncooked rice 185 g, oats 90 g, cocoa 100 g, chocolate chips 170 g, table salt 288 g (and kosher salt roughly half by volume — the salt trap that ruins conversions). The liquids anchor the logic: a cup of water weighs 240 g because a US cup is 236.6 mL and water is ~1 g/mL. Butter is the beautiful one: the wrapper markings ARE the measurements — each stick is 113.5 g = ½ cup = 8 tablespoons.
For dry ingredients, dramatically: studies of home cooks measuring flour by cup show 10–20% variance between scoops — and that is the same person, same bag, same cup. A $15 digital scale is accurate to ±1 g every time. The practical threshold: cookies and pancakes forgive; bread, macarons, and layer cakes do not — a 10% flour error is the difference between chewy and cakey. Speed bonus nobody mentions: weighing is FASTER — one bowl on the scale, tare between ingredients, zero measuring cups to wash. The conversion discipline that works: convert your five most-baked recipes to grams once (this converter + the recipe scaler), write the weights on the cards, and never scoop flour again. Baking is chemistry; chemistry runs on mass.