Why is measuring food using cups so inaccurate?
Replies
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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.)
The USDA lists a cup of whole wheat flour at 120 grams, all-purpose white flour at 120 grams and granulated white sugar at 200 grams, but you could just look at the labels of specific brands where weight is often listed along with the serving size (at least on our labels).
ETA: brown sugar is listed at 145 grams per cup unpacked and 220 packed.1 -
CafeRacer808 wrote: »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.)
This is the site I have bookmarked for baking conversions. It has the most comprehensive conversion list I have found yet.
http://www.kingarthurflour.com/learn/ingredient-weight-chart.html
Bookmarked for future reference!
I also like this butter convertor site!
http://www.traditionaloven.com/conversions_of_measures/butter_converter.html
So handy, measuring a cup of butter is silly and messy.2 -
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've been told by chefs at my college that liquids should always be weighed because it's more accurate than using a measuring jug and most liquids have a density near one, meaning their weight in grams is equal to their volume in ml. Notable exceptions are oil, hard spirits and sugar syrup - don't weigh those unless you are up for doing some maths.1 -
CattOfTheGarage 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've been told by chefs at my college that liquids should always be weighed because it's more accurate than using a measuring jug and most liquids have a density near one, meaning their weight in grams is equal to their volume in ml. Notable exceptions are oil, hard spirits and sugar syrup - don't weigh those unless you are up for doing some maths.
I use gram entries, so no maths necessary!0 -
TimothyFish wrote: »
The theory is that since a measured cup of flour may weigh a different amount than another measured cup of flour that measuring with cups is inaccurate. The irony is that the people who make this claim never demonstrate that two cups of flour that weigh the same have the same number of calories in them. There is actually inaccuracies in weighing food as well.
Wait, what?! Did you just suggest that if I weigh out 200 grams of flour, and then weigh out another 200 grams of flour, each of those 200 gram portions will have different calories? This seems pretty sketchy to me. Have you ever done a bomb calorimeter experiment, where you measure the energy released after completely combusting a substance? They measure the Calories in food with bomb calorimeters, which gives us the maximum amount of energy that can be extracted by dismantling that food. Because all foods are measured the same way, we can directly relate this to energy released by digestion because an individual will always process food with the same efficiency given their hormone/gut bacteria composition/digestive processes are constant. That covers almost everyone almost all the time outside of individuals with very specific diseases (and covers those individuals from the point of disease forward, though the ratio of measured Calories available to actual use may have changed).
Because a Calorie is a very large unit, errors in measuring grams on a typical scale (which will be in the +- 1 gram) are quite small, under 0.1% , and therefore negligible.5 -
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 actually developed myself a nice document with conversions for all the common baking items (flour, sugar, butter, brown sugar, cocoa, chocolate chips, etc.) and I convert all the recipes that sound interesting to me when I find them online and then save them in a Word document (with a link to the original recipe in case I send this Word file to anyone, so that I'm not stealing anyone's recipe!). Then, when I want to actually bake it, there it is all in grams for me!
ETA: For anyone who might find these useful, I "snipped" my conversion document into some pictures.
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VintageFeline wrote: »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.)
Or use UK recipes. Nary a cup in sight (I have one particular staple US recipe I had to go out and buy cups specifically for, they're not a staple in the UK kitchen arsenal).
Even though I've been living in the US for ten years, I still don't trust cups as a unit of measurement. Thankfully the majority of my recipe books are ones I brought over from the UK. Admittedly some of them are so ancient the measurements are in lbs rather than grams, and the oven temps are F rather than C, which led to some extremely pasty looking Cornish pasties and a Christmas cake that took nearly an entire day to cook.0 -
You don't have to weigh your food or use measuring cups at all to lose weight... unless you have trouble getting your portion sizes right and losing weight at the rate you want that is.
A scale is the more accurate tool because you can pack different amounts of food into a cup differently depending on its shape. 50 g of cheese will always be 50 g of cheese no matter if it is sliced, cubed, or shredded.
It is easier to weigh many foods like meat, cheese, yogurt, pasta, peanut butter, vegetables IMO than use measuring cups or spoons.1 -
Many times I've measured things out by cups and the food in the package never matched the servings on the label. Weighing it came closer, or at times over, the actual serving amounts. More servings per package at the right calorie amount. I'm thrifty like that sometimes.0
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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.2 -
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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