A 2 lb box of cake flour holds about 7.6 cups. The arithmetic is simple: 2 lb is 907 g, and one cup of cake flour weighs 120 g spooned and levelled, so 907 divided by 120 is 7.6 cups. Cake flour is very finely milled and low in protein, which gives cakes a tender, fine crumb — and it is sold in a 2 lb box rather than a 5 lb bag, because most home bakers use it only for cakes and go through it slowly. Seven point six cups is about three layer cakes at 2 1/2 cups per cake, or four sponge cakes at 2 cups each.
The cup weight of cake flour is a little contested: King Arthur lists 120 g per cup, but finely milled cake flour is sometimes quoted at 100 g per cup when sifted, because sifting adds air and makes the flour lighter. The difference matters: if you measure sifted cake flour by the cup, you will get less flour than the recipe expects, and the cake will be too wet. Spoon the flour into the cup and level it off, without sifting first, and the 120 g figure holds. If a recipe tells you to sift the flour, sift it after measuring, not before — that is the standard professional practice, and it keeps the measurement consistent.
Box of cake flour conversion table
The table below shows how many cups you get from fractions of a 2 lb box, and how many cups of cake flour weigh how many grams. All figures use 120 g per cup, spooned and levelled.
| Amount | Cups (approx.) | Weight |
|---|---|---|
| 1/4 bag | 1.90 cups (about 1 7/8 cups) | 227 g |
| 1/2 bag | 3.80 cups (about 3 3/4 cups) | 454 g |
| 3/4 bag | 5.70 cups (about 5 3/4 cups) | 680 g |
| Full bag | 7.60 cups (about 7 5/8 cups) | 907 g |
| Cups | Grams (approx.) |
|---|---|
| 1 cup | 120 g |
| 2 cups | 240 g |
| 3 cups | 360 g |
| 4 cups | 480 g |
| 5 cups | 600 g |
| 10 cups | 1,200 g |
Cake flour is sometimes quoted at 100 g per cup when sifted. The 120 g figure is for spooned and levelled flour, unsifted. Sift after measuring, not before, to keep the measurement consistent.
Worked examples
A birthday layer cake
A birthday layer cake for twelve people uses 2 1/2 cups of cake flour in the batter, which gives it a tender, fine crumb that a white flour cake cannot match. One 2 lb box holds 7.6 cups, so it covers three layer cakes with a little left over. Measure the flour by weight — 2 1/2 cups is 300 g — and sift it together with the baking powder and salt before adding it to the batter. Cream the butter and sugar until pale and fluffy, add the eggs one at a time, then add the flour in three parts, alternating with the milk, and mix only until combined.
A sponge cake for afternoon tea
A sponge cake for eight people uses 2 cups of cake flour, which is just over a quarter of a 2 lb box. One box covers almost four sponge cakes, which is a generous amount for a household that bakes cakes occasionally. Cake flour makes a sponge that is lighter and more delicate than one made with all-purpose flour, because the low protein content means less gluten forms. Beat the eggs and sugar until thick and pale, fold the flour in gently with a spatula, and do not overmix — the air you beat into the eggs is what makes the sponge rise.
A batch of cupcakes for a party
A batch of twenty-four cupcakes uses 2 1/2 cups of cake flour, which is a third of a 2 lb box. One box covers three batches — 72 cupcakes — which is enough for a large party. Cake flour gives cupcakes a soft, fine crumb that stays moist, and it is worth using for cupcakes even if you use all-purpose flour for everything else. Fill the cupcake cases two thirds full, bake at 175°C for 18 to 20 minutes, and test with a skewer: it should come out clean, with no wet batter clinging to it.
How the figure is worked out
Think of the answer as a conversion, not a measurement. The package weight is a standard 2 lb (907 g) box of cake flour. One cup of this ingredient weighs a known number of grams, so the cups in the package are the package weight divided by the cup weight. The method matters as much as the number: a spooned and levelled cup is the standard, and a scooped cup packs in more, which is why two bakers can get different cup counts from the same bag. The cup weight used here is 120 g per cup, spooned and levelled, sourced from King Arthur Baking. King Arthur lists 120 g per cup; finely milled cake flour is sometimes quoted at 100 g per cup when sifted, so spoon and level rather than scooping.
Practical guidance
Cake flour is a specialist flour, and it is worth using for cakes even though it costs more than all-purpose flour. The fine milling and low protein content — about 7 to 9 percent, compared with 11 percent for all-purpose — produce a tender crumb that is hard to achieve any other way. If you do not have cake flour, you can approximate it by replacing 2 tablespoons of all-purpose flour per cup with cornstarch, but the result is not identical: the homemade version is close, but real cake flour is finer and gives a better texture. For a cake that matters — a birthday, a wedding — use the real thing.
Measure cake flour by weight, and sift after measuring. The fine milling means cake flour packs more easily than other flours, so a scooped cup can weigh significantly more than 120 g, and the cake will be dense and dry. Spoon it into the cup, level it off, and then sift it with the other dry ingredients. Store cake flour in an airtight container in a cool, dry place for up to a year, and freeze it for 48 hours when you buy it to kill any pantry moth eggs. A 2 lb box lasts a long time if you only bake cakes occasionally, so check the date before you use it — stale cake flour makes a stale-tasting cake.
Frequently asked questions
How many cups are in a 2 lb box of cake flour?
About 7.6 cups. A 2 lb box is 907 g, and at 120 g per cup that divides out to 7.55 cups. That is about three layer cakes at 2 1/2 cups each, or four sponge cakes at 2 cups each.
Why is cake flour sometimes quoted at 100 g per cup?
Because sifting adds air and makes the flour lighter. Finely milled cake flour, sifted, can weigh about 100 g per cup. The King Arthur figure of 120 g is for spooned and levelled flour, unsifted. To keep the measurement consistent, measure first and sift afterwards.
Can I substitute all-purpose flour for cake flour?
Yes, with an adjustment: replace 2 tablespoons of all-purpose flour per cup with cornstarch, and sift the mixture together. The result is close to cake flour but not identical — real cake flour is finer and gives a more tender crumb. For an everyday cake the substitution is fine; for a special cake, use real cake flour.
How long does cake flour keep?
Up to a year in an airtight container in a cool, dry place. Cake flour is white flour, so it keeps longer than whole wheat flour. Freeze it for 48 hours when you buy it to kill pantry moth eggs, and check the date before using a box that has been open for a long time.
What is cake flour best for?
Layer cakes, sponge cakes, cupcakes, chiffon cakes and any cake where a tender, fine crumb matters. It is not suitable for bread or pizza, where the low protein content means the dough will not develop enough gluten, and it is a poor choice for cookies that need structure.