When it comes to baking, accuracy in your measurements is critical to a recipe’s success, and the single most accurate way to measure your ingredients is by weight.
I’ve received a few questions lately on some of my more popular cake recipes that seem to imply some confusion about weight versus volume measurements, specifically when it comes to measuring dry ingredients like flour. I figured I’d do a bit more in-depth explanation in a post, to hopefully clear up any confusion.
American bakers grew up using cups, where a cup of water is equal to a cup of flour and so forth. We also had it drilled into our brains that a cup is 8 ounces and a pint is a pound the world round (a pint being two cups or 16 fluid ounces).
But I’m here to say that a pint is NOT always a pound and a cup is NOT always 8 ounces—it depends on what you’re measuring.
Now before you start arguing, let me explain!
Weight versus Volume
Volume is a measure of the amount of space something takes up. Things like cups of flour, gallons of milk, cubic feet of helium… these are all volume measurements.
Weight is a measurement of an object’s heaviness. Grams of salt, pounds of sugar, kilograms of apples… these are measurements of weight.
Ok. So, that makes sense, right? Volume and weight are measuring two entirely different things.
You’ve heard the old riddle: Which weighs more: a pound of feathers or a pound of lead?
Trick question: they both weigh a pound! BUT the lead is going to have a much smaller volume since it is more dense than the feathers, so it will look like a smaller amount of material.
When we’re talking about baking, the differences might not be quite as apparent as feathers and lead, but the same is true of flour and water: one is much less dense than the other (in this case the flour is the feathers and the water is the lead). So a pound of flour is going to take up more space, or volume, than an equivalent pound of water.
An Ounce of Confusion
Most of the confusion regarding weight and volume measurements occurs when talking about ounces: an imperial unit of measurement which can be used to indicate both weight AND volume. Fluid ounces refers to volume (like milliliters) whereas regular ounces refer to weight (like grams). The fact that they are both called ounces, and not always differentiated by saying ounce/fluid ounce is one reason why they are so problematic.
Ounces by weight and ounces by volume are ONLY comparable when you are measuring water or other liquids with a similar density.
For example, 8 ounces of water by weight will equal 8 fluid ounces by volume.
Flour, on the other hand, is a totally different ballgame and a confusing one to boot. Not that you’d ever measure flour with fluid ounces (which are only designed to measure—you guessed it—fluids), but, if you did, you’d find that 8 fluid ounces of flour only weighs about 4 1/4 ounces. Weigh out 8 ounces of flour by weight and you’re going to have about 14 fluid ounces by volume. See how confusing it is?
I mean, who do we need to petition to have fluid ounces changed to be called something totally different (flounces? frams? vols?) or, better yet, finally just switch to metric like the rest of the world?
Anyway.
Here are some visual comparisons to help illustrate this concept (keep in mind that you shouldn’t be measuring flour in a liquid measuring cup like this, I only did so here so I could illustrate the differences between ounces by weight and ounces by volume).
Both of these containers are holding 8 ounces.
On the left is 8 ounces of flour by weight, and on the right is 8 ounces of flour by volume (aka 1 cup).
If you weighed the two containers, the one on the right would only weigh approximately 4 1/4 ounces.
Both of these containers are holding 8 ounces.
Weigh out 8 ounces of flour and 8 ounces of water on a scale and this is what you get. Visually it looks like you have a lot more flour than water, but they weigh the exact same amount.
Both of these containers are holding 8 ounces.
On the left is 8 ounces of flour by volume and on the right is 8 ounces of water by volume. Basically, what you see here is 1 cup of flour and 1 cup of water.
But if you put these two containers on a scale, the flour on the left would only weigh 4 1/4 ounces, while the water would weigh 8 ounces.
So, are you less confused yet? More confused? I don’t blame you (lol).
My advice? When you’re baking, forget ounces entirely. Pretend they don’t even exist. It just confuses things. Instead, focus on cup/tablespoon measurements for volume, and grams for weight.
I’m trying to be better about writing my recipes using just cups and grams for this very reason, though you may still see ounces on older recipes or for things that are sold by the ounce, like bars of chocolate or cans of pumpkin.
Tip: When purchasing packaged or canned goods, if you’re unsure whether the ounce measurement on the package refers to ounces by weight or fluid ounces, look at the metric equivalent. If it’s grams (like on canned pumpkin or chocolate bars), you’re dealing with weight. If it’s liters (like on milk or wine) then you’re dealing with fluid ounces.
The Beauty of Metric
One of the beautiful things about the metric system is that there is no confusion. Grams are weight, milliliters are volume. If you see grams, grab your scale. If you see milliliters, grab your liquid measuring cup.
Another genius aspect of the metric system is that it is calibrated to water: so when you’re measuring water or other liquids with a similar density (like milk or orange juice), 200 milliliters will weigh 200 grams. Cool!
However, once you start measuring dry ingredients, which often have varying densities, the two numbers will not match.
1 cup of water weighs 236 grams.
1 cup of flour weighs 125 grams.
The volume is the same, but the weight is different (remember: lead and feathers).
One other benefit to using metric measurements is accuracy: scales often only show ounces to the quarter or eighth of an ounce, so 4 1/4 ounces or 10 1/8 ounces. Grams on the other hand, being a much smaller unit of measurement, make it easier to be incredibly precise. Exactly 236 grams of water is a much more accurate measurement than 8 3/8 ounces (technically 236 grams equals 8.32466 ounces but you’re not going to be able to measure that on a scale). The difference of 1/8th of an ounce is 3-4 grams, which may not seem like much, but it can add up.
A cup is a cup is a cup
… depending on what you’re measuring and how you measure it.
Liquids are pretty reliable. A cup is pretty much always going to be a cup.
But for dry ingredients, flour specifically, the small granules of flour can be compacted, essentially packing more flour into the same amount of space (think about packing brown sugar, it’s a similar idea).
So depending on how you measure your flour, if you fluff it and spoon it into the cup, or if you scoop directly from a bag of flour that has settled, your ‘cup’ may vary by as much as 30% by weight, from 120 grams to upwards of 150 grams (!!) When you’re making a cake that calls for 3 cups of flour, that’s almost an entire extra cup if you’re scooping directly from the bag. No wonder the cake is too dry…
Here you can see what I mean. The cup on the left was measured using the fluff, spoon and sweep method, while the one on the right was scooped right out of the bag. 125 grams and 146 grams may not seem like a big difference, but it can mean the difference between a perfectly moist chocolate cake and a dry one.
The best way to measure flour is…
With a scale! In grams! (If you’ve read this far you probably guessed that.)
However, I know that’s not always going to happen. We’re so used to baking with cups that getting out the scale feels like a chore. And, while I’ve acclimated myself to using mainly weight-based measurements, I acknowledge that it is not for everyone.
If you’re going to continue to use cups, it’s helpful to know the best method for measuring a perfect cup of flour: one that’s actually a true cup and not a compacted one.
My favorite method: fluff, spoon and sweep.
First, fluff up your flour by stirring it in the bag (or, better yet, pour it out of the bag into a large canister which will do a great job of aerating on its own).
Then, spoon flour and sprinkle it into your measuring cup. Don’t scoop flour directly into the measuring cup, which can compact it. Rather, get a big spoonful of flour and sprinkle it into the measuring cup.
Once you’ve got a heaping pile of flour in the measuring cup, sweep off the excess using a straight-edge like the back of a butter knife or offset spatula to level off the top of the cup.
Try this out a few times with a scale handy, and see what weight you get for 1 cup of flour. You should see about 125 grams of flour per level cup. If you are getting 130 grams or higher, you might want to revisit your method (maybe you’re not fluffing it enough, or maybe you are compacting the flour when you level it, or maybe your measuring cups are off.)
Now just for comparison, go scoop a big cup of flour right out of a bag. Really dig your cup in there. Level off the top, then weigh the flour. Notice a difference? I bet you will! Those extra 30 or more grams of flour can really make a difference when baking, as extra flour can lead to dry or dense cakes and cookies.
Cocoa powder is another ingredient that can be compacted, so using either weight or the fluff, scoop and sweep method is useful here as well.
Liquid versus Dry Measuring Cups
Unless you only bake with weight-based measurements exclusively, you should have two kinds of measuring cups in your kitchen: liquid measuring cups and dry measuring cups, and you should use each accordingly. Don’t pour liquids into dry measuring cups, and likewise don’t try to measure flour in a liquid measuring cup. Simply put, you’re not going to get accurate results.
Liquid measuring cups are clear, with marks on the side of the cup indicating the volume of liquid in cups, ounces and milliliters. The ounce markers here refer to fluid ounces, and for water-like liquids the ounces by weight will equal the ounces by volume. However for liquids of different densities, say, sweetened condensed milk, for example, 1 cup or 8 fluid ounces will actually weigh 10 ounces on a scale.
Dry measuring cups and spoons should be labeled with only the dry volume quantity, such as 1/2 cup or 1 tablespoon. If you find yourself with a set of dry measuring cups that also lists grams or ounces on them, either teach yourself to ignore those numbers entirely (they’re only relevant for liquids, which you shouldn’t be measuring with dry cups anyway)… or buy a new set of measuring cups altogether.
Why can’t you measure dry ingredients in liquid measuring cups? Well, it’s hard to get them level. If you spoon some flour into a liquid measuring cup, the top is going to be uneven. So maybe you shake it a bit to try to level out the top, but you’re really just compacting the flour even more. With a dry measuring cup, you can perfectly level off the top using a knife or other straight edge, making sure you have exactly the amount you need.
Why can’t you measure wet ingredients in dry measuring cups? Well, you can, sort of, but you’ll probably make a mess of it. Because to get a proper measurement you have to fill the cup full to the brim with the liquid. Good luck trying to move it to your bowl without spilling…
Technically even liquids like vanilla extract should be measured in a liquid measurer, although for such small amounts like this it is not critical (it’s reasonably easy to measure out 1 teaspoon of vanilla in a spoon without spilling it). I like this beaker measuring set for that reason.
Liquids aren’t quite as problematic as dry ingredients, as you can’t ‘compact’ the molecules of, say, milk the way you can with flour. So a cup of milk is going to be pretty consistent in terms of volume and weight. Just remember that the ounces printed on your liquid measuring cups are fluid ounces, which aren’t always equal to ounces by weight.
Tip: Weigh your empty mixing bowl and write that number on the bottom of the bowl with a sharpie. Then you know the tare weight of the bowl even if you forget to tare your scale before adding ingredients.
But the gold standard of measurement regardless of what you’re measuring is to weigh out everything with a kitchen scale in grams. You simply cannot measure weight with volume-based measuring cups. Measuring by weight means you don’t have to deal with measuring cups at all (hooray for fewer dishes!)
Common Ingredient Weights
- All Purpose Flour: 1 cup = 125 grams
- Cocoa Powder: 1 cup = 120 grams
- Sugar: 1 cup = 200 grams
- Brown Sugar: 1 cup = 220 grams
- Butter: 1 cup = 226 grams
- Water: 1 cup = 236 mL/236 grams
- Milk/Cream: = 240 mL/240 grams
The more you bake by weight, you’ll start to memorize these common conversions until you no longer have to look them up!
I’d suggest picking up a copy of The Baker’s Appendix which has listings of dozens of common ingredients and their equivalent weights (I use these values as reference points when writing recipes). You can also use a resource like King Arthur Flour’s Master Weight Chart as well (print out a copy, laminate it and stash it behind your flour canisters).
Do note that different sources do list different base weights, for example King Arthur lists 1 cup of flour at 120 grams and The Baker’s Appendix says 125 grams.
When in doubt, follow the recipe!
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