Why does my flour weigh less than the same volume of water?

All-purpose flour has a bulk density around 0.53 g/ml — about half that of water (1 g/ml). The gaps between grains take up almost as much space as the flour itself, so a cup of flour weighs much less than a cup of water.

Which cup are we using?

The US legal cup of 236.588 ml is the default. The "metric cup" of exactly 250 ml is listed separately because it's the standard in Australia and some recipe books. UK Imperial cups (284 ml) aren't included — they're rare outside very old UK cookbooks.

How accurate are the ingredient densities?

Within roughly ±10 % for most pantry items. Flour and powdered sugar in particular vary a lot with sifting and packing — for precision baking, weigh on a scale rather than relying on a volume conversion.

Cooking Conversions

Volume conversions across the US cup / tbsp / tsp / fl oz family and metric ml / l, plus the alternate 250 ml "metric cup". When you pick an ingredient (flour, sugar, butter, honey, …), the tool also weighs your amount in grams, kilograms, ounces, and pounds using a published bulk density. Densities are approximations — real ingredients vary with brand, humidity, and how packed the spoonful is.

—

AmountFromIngredient (for weight)

Volume

ml237
l0.237
tsp48.0
tbsp16.0
fl oz8.00
cup1.00
pint0.500
quart0.250
gallon0.062
metric cup0.946

Weight

g125
kg0.125
oz4.42
lb0.276

Densities are approximations — for precision baking, weigh on a scale.

How to use

Enter an amount and pick the unit it's in (cup, tbsp, ml, …).
Pick an ingredient to also see the weight in g / kg / oz / lb. Leave it blank for a volume-only table.
Read off the equivalent in whichever unit your recipe wants.

Frequently asked questions

Why does my flour weigh less than the same volume of water?: All-purpose flour has a bulk density around 0.53 g/ml — about half that of water (1 g/ml). The gaps between grains take up almost as much space as the flour itself, so a cup of flour weighs much less than a cup of water.
Which cup are we using?: The US legal cup of 236.588 ml is the default. The "metric cup" of exactly 250 ml is listed separately because it's the standard in Australia and some recipe books. UK Imperial cups (284 ml) aren't included — they're rare outside very old UK cookbooks.
How accurate are the ingredient densities?: Within roughly ±10 % for most pantry items. Flour and powdered sugar in particular vary a lot with sifting and packing — for precision baking, weigh on a scale rather than relying on a volume conversion.

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