When it comes to baking, accuracy in your dimensions is crucial to a recipe’s success, and also the single most accurate method to measure her ingredients is by weight.

You are watching: Weight of a cup of water

I’ve obtained a few questions recently on some of my an ext popular cake recipes that seem to indicate some confusion about weight matches volume measurements, specifically as soon as it concerns measuring dried ingredients choose flour. I figured I’d carry out a bit much more in-depth explanation in a post, to hopefully clear up any confusion.

American bakers thrived up utilizing cups, where a cup that water is equal to a cup of flour and also so forth. We also had the drilled right into our brains that a cup is 8 ounces and a pint is a pound the human being round (a pint being two cups or 16 fluid ounces).

But I’m right here to say the a pint is NOT constantly a pound and also a cup is NOT always 8 ounces—it counts on what you’re measuring.

Now before you begin arguing, let me explain!

Weight matches Volume

Volume is a measure up of the amount of an are something takes up. Things like cups that flour, gallons the milk, cubic feet that helium… these are all volume measurements.

Weight is a measurement of an object’s heaviness. Grams that salt, pounds the sugar, kilograms of apples… this are measurements of weight.

Ok. So, that renders sense, right? Volume and weight space measuring 2 entirely various things.

You’ve heard the old riddle: Which weighs more: a lb of feather or a pound of lead?

Trick question: lock both sweet a pound! yet the command is walk to have actually a much smaller volume since it is more dense 보다 the feathers, for this reason it will look prefer a smaller sized amount that material.

When we’re talking about baking, the differences can not be quite as evident as feathers and also lead, yet the exact same is true of flour and also water: one is lot less thick than the various other (in this instance the flour is the feathers and also the water is the lead). So a lb of flour is going to take it up much more space, or volume, 보다 an equivalent pound of water.

An oz of Confusion

Most that the confusion regarding weight and volume measurements occurs once talking around ounces: an royal unit of measurement which have the right to be offered to show both weight and volume. Fluid ounces refers to volume (like milliliters) whereas continual ounces describe weight (like grams). The truth that they room both referred to as ounces, and also not constantly differentiated by saying ounce/fluid ounce is one reason why they room so problematic.

Ounces by weight and also ounces through volume room ONLY comparable when you are measuring water or other liquids with a comparable density.

For example, 8 ounces the water by weight will certainly equal 8 liquid ounces by volume.

Flour, on the other hand, is a completely different ballgame and also a confuse one come boot. Not that you’d ever before measure flour with fluid ounces (which are only designed to measure—you guessed it—fluids), but, if friend did, you’d uncover that 8 fluid ounces the flour only weighs about 4 1/4 ounces. Sweet out 8 ounces of flour by weight and you’re going to have about 14 liquid ounces through volume. See just how confusing it is?

I mean, who do we need to petition come have liquid ounces readjusted to be dubbed something totally different (flounces? frams? vols?) or, far better yet, finally just switch to metric prefer the rest of the world?

Anyway.

Here space some visual comparisons to aid illustrate this principle (keep in mind that you shouldn’t be measuring flour in a liquid measuring cup choose this, I just did so below so I can illustrate the differences in between ounces by weight and also ounces by volume).

Both of these containers room holding 8 ounces.

On the left is 8 ounces of flour by weight, and on the right is 8 ounces that flour by volume (aka 1 cup).

If you weighed the two containers, the one ~ above the right would only weigh around 4 1/4 ounces.

Both of these containers are holding 8 ounces.

Weigh the end 8 ounces that flour and also 8 ounces the water ~ above a scale and this is what friend get. Visually that looks prefer you have actually a lot more flour 보다 water, yet they sweet the precise same amount.

Both of this containers space holding 8 ounces.

On the left is 8 ounces that flour by volume and on the best is 8 ounces of water through volume. Basically, what girlfriend see right here is 1 cup that flour and 1 cup that water.

But if you put these two containers ~ above a scale, the flour ~ above the left would only weigh 4 1/4 ounces, when the water would weigh 8 ounces.

So, space you less perplexed yet? more confused? i don’t blame friend (lol).

My advice? as soon as you’re baking, forget ounces entirely. Pretend lock don’t also exist. It simply confuses things. Instead, focus on cup/tablespoon measurements for volume, and grams because that weight.

I’m trying come be far better about composing my recipes using just cups and grams because that this really reason, despite you might still watch ounces on older recipes or for points that are marketed by the ounce, like bars of chocolate or cans of pumpkin.

Tip: when purchasing packaged or canned goods, if you’re unsure even if it is the oz measurement ~ above the package refers to ounces by weight or liquid ounces, look at the metric equivalent. If it’s grams (like on crate pumpkin or coco bars), you’re taking care of weight. If it’s liters (like on milk or wine) then you’re dealing with fluid ounces.

The beauty beauty of Metric

One the the beautiful things about the metric system is that there is no confusion. Grams space weight, milliliters are volume. If you see grams, grab your scale. If you check out milliliters, grab your liquid measuring cup.

Another genius element of the metric device is that it is calibrated to water: so as soon as you’re measuring water or other liquids through a similar density (like milk or orange juice), 200 milliliters will weigh 200 grams. Cool!

However, once you begin measuring dry ingredients, which often have differing densities, the 2 numbers will certainly not match.

1 cup of water weighs 236 grams.1 cup the flour weighs 125 grams.

The volume is the same, but the weight is various (remember: lead and feathers).

One other benefit to using metric dimensions is accuracy: scales frequently only display ounces come the 4 minutes 1 or eighth of an ounce, therefore 4 1/4 ounces or 10 1/8 ounces. Grams ~ above the various other hand, being a much smaller unit of measurement, make it much easier to be extremely precise. Exactly 236 grams that water is a much an ext accurate measurement than 8 3/8 ounces (technically 236 grams amounts to 8.32466 ounces yet you’re not going to have the ability to measure that on a scale). The difference of 1/8th that an oz is 3-4 grams, which may not seem prefer much, but it can include up.

A cup is a cup is a cup

… relying on what you’re measuring and also how you measure up it.

Liquids room pretty reliable. A cup is nice much always going to be a cup.

See more: Which Organelles Comprise The Endomembrane System Of A Cell Chapter 4 Flashcards

But because that dry ingredients, flour special, the small granules the flour deserve to be compacted, essentially packing much more flour into the same amount of room (think about packing brown sugar, it’s a similar idea).

So depending upon how you measure your flour, if friend fluff it and spoon it into the cup, or if friend scoop directly from a bag of flour that has actually settled, her ‘cup’ might vary through as lot as 30% by weight, indigenous 120 grams to upwards of 150 grams (!!) once you’re do a cake that calls because that 3 cups of flour, that’s virtually an entire extra cup if you’re scooping straight from the bag. No wonder the cake is as well dry…