Why is measuring food using cups so inaccurate?
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And lets not forget that not all dry measuring cups are created equal. I had two sets of them. One was a cheapo plastic set from my college days, the other a metal set from a professional baking supply company. Even before I got a food scale, it was obvious that 1 c. was not the same between the two sets and which set was more accurate based on baking results.
I ended up re-purposing the plastic ones as scoops. I'll still measure with the metal ones occasionally - they're plenty accurate for good baking results with flour, sugar, etc. Never more than a couple of grams off when I do a double check.
For some reason this reminds me of when someone asked me if they could use silverware teaspoons and soup spoons to measure baking soda, etc.0 -
And lets not forget that not all dry measuring cups are created equal. I had two sets of them. One was a cheapo plastic set from my college days, the other a metal set from a professional baking supply company. Even before I got a food scale, it was obvious that 1 c. was not the same between the two sets and which set was more accurate based on baking results.
I ended up re-purposing the plastic ones as scoops. I'll still measure with the metal ones occasionally - they're plenty accurate for good baking results with flour, sugar, etc. Never more than a couple of grams off when I do a double check.
Also cup measures are different sizes in different places. My cup measures are based around a 250ml cup - a "metric" cup, I suppose you could call it. But an American cup and an old UK Imperial cup are both different from this and from each other. I don't think it stops there, either, I think there are more different definitions of a cup in other areas of the world.
It's odd, in any case, to call it a "cup". Our actual cups (the china teacups we keep for unexpected visits by royalty) are about 150ml. A "cup" in measurements is huge, more like a coffee mug.0 -
CattOfTheGarage wrote: »There's also the fact that many cup measures have the line below the top rim, so you are supposed to fill them level to slightly below the rim. There is just so much room to heap it slightly or fill it just a little bit too deep and so create an error.
To be nerdy about it:
Those kinds of measuring cups are intended for measuring liquids. You cannot "heap" liquids, and proper use of a liquid measuring cup requires you to place it on a level surface and put yourself at eye level with whatever line indicates the amount you want to ensure the liquid is at the line, not over it.
A cup (or fraction of a cup or multiple of a cup) for measuring solids is supposed to allow for exactly the volume it says it is (that is, the food fill the up without going over), so "heaping" should be fairly obvious.
That said, I agree that there is still so much scope for error or "cheating" in the size of the individual "pieces" of whatever solid you're measuring (even the variations in coarseness for things like flours and meals), which affects how much air is in the volume you're measuring, that you'll get better accuracy for the purposes of calorie counting (or following a recipe) by weighing your solids.
And, as you say, the practice of weighing can greatly improve your "eyeballing" proficiency -- I'm reasonably confident that I'm within 25% when I guesstimate amounts when eating out or at someone else's home, or on those rare occasions at home when I forget to tare or to jot down an amount or do something else that leaves me without a measured weight to record.
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estherdragonbat wrote: »Ok. So, I do a fair bit of baking and baking being a science, rather than an art, how many grams of flour, sugar, baking powder, etc should I use if the recipe calls for a cup? (Baking powder isn't bugging me that much; most recipes I make don't call for more than a teaspoon, so the calories per serving will be negligible. White and whole wheat flour and white and brown sugar are the biggies.)
I use the information on the label of the product (e.g., if the flour label lists a serving as 1/4 cup (30 g), and the recipe calls for 3 1/2 cups of flour, I use 420 g of flour [3 1/2 cups = 14 quarter-cups; 14 X 30 = 420]). (Of course, if it's bread, it's just easier to weigh the sack of flour before you start using it, because you're going to have to add some indeterminate amount as you knead it.)0 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Cups are an American idea. The rest of us don't measure for recipes by the cup.
The real reason though is that a cup is a unit of volume, not of mass. So a cup of a dense item will take up the same space as a cup of a fluffier item, but be a completely different mass or weight. Think of a sandbag and that same bag filled with feathers.0 -
amusedmonkey wrote: »Cups are great for liquid measure, but inaccurate for most dry goods. The density varies so greatly in many products. A cup of flour will increase in weight on a humid day and decrease on a dry day. Commercial bakeries always use the weight of dry ingredients when preparing a mixture.
I even weigh my liquids, because who has time for extra dishes?
I do this too for liquids that the USDA offers nutritional information based on weight (like milk of a particular fat%), but the labels on most containers for liquids only give a volume serving size.
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Or 2 tablespoons of almonds? Or 2 cups of salad?cwolfman13 wrote: »What does 1 cup of chicken look like?
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lynn_glenmont wrote: »amusedmonkey wrote: »Cups are great for liquid measure, but inaccurate for most dry goods. The density varies so greatly in many products. A cup of flour will increase in weight on a humid day and decrease on a dry day. Commercial bakeries always use the weight of dry ingredients when preparing a mixture.
I even weigh my liquids, because who has time for extra dishes?
I do this too for liquids that the USDA offers nutritional information based on weight (like milk of a particular fat%), but the labels on most containers for liquids only give a volume serving size.
For anything water-based, 1 g = 1 mL (or close enough; 15 g/tbsp). Fats/oils don't follow that rule; they're usually close to 9 g = 10 mL (~14 g/tbsp). Alcohol is about 8 g = 10 mL (12 g/tbsp). Syrups/honey are about 14 g = 10 mL (~20 g/tbsp).
I am obviously assuming 15 mL tablespoons. If your tablespoons are larger/smaller, use the g = mL numbers.1 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Cups are an American idea. The rest of us don't measure for recipes by the cup.
The real reason though is that a cup is a unit of volume, not of mass. So a cup of a dense item will take up the same space as a cup of a fluffier item, but be a completely different mass or weight. Think of a sandbag and that same bag filled with feathers.
To be historically accurate, the cup comes from the imperial system of measurement, which was British. Most Commonwealth nations used it prior to adaptation of the metric system. It is 1/2 a pint, or 2 gills.1 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Cups are an American idea. The rest of us don't measure for recipes by the cup.
The real reason though is that a cup is a unit of volume, not of mass. So a cup of a dense item will take up the same space as a cup of a fluffier item, but be a completely different mass or weight. Think of a sandbag and that same bag filled with feathers.
To be historically accurate, the cup comes from the imperial system of measurement, which was British. Most Commonwealth nations used it prior to adaptation of the metric system. It is 1/2 a pint, or 2 gills.
Even more historically accurately, it's from the English system of measurement. The Imperial system wasn't promulgated until after America won its independence, and America never adopted it. In most cases, such as measures of length, it doesn't make a difference, but since we're talking about volume it makes a big difference because America settled on a different standard than the UK. Pints are not the same size between the two; the American pint is significantly smaller. (But the American ounce is larger. British pints are 20 oz, not 16, so their pints come out larger even though their ounces are smaller.)
In fact, the measuring cup wasn't invented until 1896, while the Imperial system was promulgated in 1825. So the cup cannot have come from the Imperial system.0 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Cups are an American idea. The rest of us don't measure for recipes by the cup.
The real reason though is that a cup is a unit of volume, not of mass. So a cup of a dense item will take up the same space as a cup of a fluffier item, but be a completely different mass or weight. Think of a sandbag and that same bag filled with feathers.
To be historically accurate, the cup comes from the imperial system of measurement, which was British. Most Commonwealth nations used it prior to adaptation of the metric system. It is 1/2 a pint, or 2 gills.
Not really in terms of cooking culture. Old UK cookbooks use pounds and ounces for solids, even going back quite far, and before that point you're into hopelessly vague old recipes with "a handful of flour" and "sufficient lard".
We never really used cup measures for cookery except very occasionally - volumetric measures were only for liquids and they tended to be pints and fluid ounces, not so much cups.
The basic assumption for a long time in the UK has been that the cook owns a scale and will use it. A kitchen without a scale in the UK is highly unusual and means the owner does not cook at all.5 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Take a cup of Rice Krispies compared to a cup of say All Bran. The cup of All Bran will be considerably heavier.1 -
GoCleanGoLean wrote: »You know how people say to always weigh their food instead of using measuring cups to judge how much you're eating? Well I was wondering why measuring cups are so inaccurate. Like it makes sense that using a measuring cup to measure out 1 cup of flour could cause some discrepancy depending on how much the flour is packed down.
But what about foods that aren't so easily smushed such as cereal? Or others food like that. Is using a measuring cup that inaccurate? Do I really need a food scale to weigh out how much cereal I'm eating?
Cups are an American idea. The rest of us don't measure for recipes by the cup.
The real reason though is that a cup is a unit of volume, not of mass. So a cup of a dense item will take up the same space as a cup of a fluffier item, but be a completely different mass or weight. Think of a sandbag and that same bag filled with feathers.
To be historically accurate, the cup comes from the imperial system of measurement, which was British. Most Commonwealth nations used it prior to adaptation of the metric system. It is 1/2 a pint, or 2 gills.
Interesting. I never thought the metric system had any impact on it. For sure, the difference between liquid and solid measurement seems more clear cut in metric.0 -
It is usually inaccurate because people jam a lot into a measuring cup. Think of packed brown sugar vs. brown sugar spooned into a cup, only just reaching the top of it. Most labels give you the nutrition info for a quantity of food similar to the loosely spooned brown sugar. Most people like to jam as much as possible into the cup, sometimes even spilling over the side and certainly heaped up top.
This0 -
Seeing a lot of reasoning about why one cup of X weighs more than the next. For some substances, it's built in to the nature of the substance, not about whether we pack, level, choose a different type of cereal (whose box should have a weight per cup that reflects that variety of cereal, BTW, even though it may differ from the weight of your cup of the same cereal).
Oatmeal: Plain, regular old-fashioned rolled oats. I eat 30g (dry) most days. It's around 1/4 cup . . . but will vary from a bit below the cup's rim, to very heaping. (I use a 1/4 cup measure as a scoop - weigh the container of oats, zero, scoop, note negative value). Tends to be similar volume for each batch of oats bought from the bulk section of my store, but varies between batches. Shrug.
Gonna be even worse with, say, English walnut halves and pieces, depending on how "piece-y" they are.2 -
Want a real shock and disappointment? Weigh that serving of peanut butter that you've been eyeballing as 2 tablespoons.3
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