How this instrument works
A pound of flour and a pound of butter don't fill the same number of cups, because pounds measure weight and cups measure volume, and how densely an ingredient packs into a cup is entirely its own property. Butter, for one exceptional case, has a genuinely fixed relationship to cups rather than an approximate one: it's sold in 1-lb boxes of four sticks, and each stick is defined as exactly 1/2 cup, which makes '1 lb of butter equals 2 cups' a packaging fact, not an estimate.
This instrument divides your pound amount, converted to grams, by the selected ingredient's standard weight per cup — 120 g for all-purpose flour, 200 g for granulated sugar, 220 g for packed brown sugar, or 227 g for butter, all figures drawn from widely used baking references. Selecting a different ingredient changes the cup result meaningfully, since these reference weights vary by close to double across the four options.
For flour and sugar, these are standard reference weights, not physical constants — how tightly an ingredient is packed into the cup (spooned in lightly versus scooped straight from the bag) can shift the true weight by 10% or more, especially for flour. Butter is the one exception here: its cup relationship is fixed by how it's packaged, so that particular conversion is exact rather than a baking approximation.
- Enter the weight in Pounds you're converting.
- Select the Ingredient — all-purpose flour, granulated sugar, packed brown sugar, or butter — each with its own reference weight per cup.
- Read Cups — the volume that weight fills for the ingredient chosen.
- For flour, spoon it lightly into the cup and level it off rather than scooping from the bag, which packs in extra flour and shifts the weight-to-cup relationship this calculator assumes.
Worked example — 1 lb of butter
A recipe calls for 1 lb of butter, and the cook wants to know it in cups. Converting the weight: 1 × 453.59237 = 453.59237 g, divided by butter's 227 g/cup reference: cups = 453.59237 ÷ 227 = 1.99820 cups.
That's about 2 cups — and it's not a coincidence or rounding error, since butter's true cup relationship is exact by packaging: a 1-lb box holds exactly 4 sticks, and each stick is defined as exactly 1/2 cup, so 1 lb of butter is exactly 2 cups. The tiny 0.09% gap from a perfectly round 2.00 here comes from 227 g being a slightly rounded reference weight for that packaging fact, not from any real-world variation in the butter itself.
Questions
Is 1 lb of butter really exactly 2 cups?
Yes — unlike flour or sugar, butter's cup relationship isn't a baking approximation, it's fixed by how butter is packaged: a standard 1-lb box contains 4 sticks, and each stick is defined as exactly 1/2 cup, wrapper markings and all. This calculator's 227 g/cup reference weight is a very close, standard rounding of that exact packaging fact, landing at 1.998 rather than a perfectly round 2.00 cups for 1 lb.
Why is packed brown sugar heavier per cup than granulated sugar?
Because 'packed' is part of the measurement instruction — brown sugar is pressed firmly into the cup until it holds the cup's shape when turned out, which squeezes out more of the air between grains than granulated sugar's looser measuring convention. That denser packing is why brown sugar's reference weight (220 g/cup) runs higher than granulated sugar's (200 g/cup), even though the two aren't wildly different substances.
Why does flour convert so differently from sugar for the same pound?
Flour is much lighter per cup than sugar — its reference weight is 120 g/cup versus sugar's 200 g/cup, so the same pound of flour fills noticeably more cups than the identical pound of sugar. This comes down to how the two ingredients' particles pack: flour's fine, powdery structure traps more air between particles than sugar's denser granules.
Should I scoop or spoon flour when measuring by cups?
Spoon it in lightly and level it off with a knife, rather than scooping the measuring cup directly through the flour bag — scooping compacts the flour and can pack in 20-25% more than the spoon-and-level method most baking references (including this calculator's 120 g/cup figure) assume. That difference is large enough to noticeably change a baked good's texture if it happens consistently.
Does this calculator work for ingredients other than the four listed?
No — it only holds reference weights for all-purpose flour, granulated sugar, packed brown sugar, and butter, since every other ingredient has its own distinct weight-per-cup figure. For anything else, you'd need that specific ingredient's own reference weight, often available on packaging or in a dedicated baking ingredient chart.