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I don't have a big jar to put my flour in so it's hard to measure by volume (you have to fluff the flour, pour it into a cup and then remove the excess - which cant be done outside of the original bag).

It it okay to just look up the conversion (for example, 1 cup of flour is 120 grams) and use that?

jscs
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Bar Akiva
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  • I've tried to ask a more specific variation of this question, about what conversion to actually use, not just whether it's okay to weigh: https://cooking.stackexchange.com/questions/87324/how-should-i-pick-an-initial-guess-for-converting-flour-volume-to-weight – Cascabel Jan 26 '18 at 19:37

3 Answers3

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Short answer: YES. Measuring by weight is actually the better way to measure flour.

In fact, measuring flour by weight is the preferred method of measuring it in most places. This is because while measuring by volume is more convenient*, measuring by weight is more accurate. If you weigh your flour, however, you will always know you are using the same amount, whereas two individually measured cups of flour (done by volume) can have wildly different weights. This makes recipes where you measure by volume much harder to repeat reliably and perfect with small tweaks.

For a more detailed reference on converting cups of flour to grams, see this answer. As noted in the answers to that question and in the comments below, the average weight of a cup of flour can vary greatly, between 4 and 5 ounces (about 110 to 140 grams), though a heavily packed cup could weigh much more. I personally use 1 cup = 4.5 ounces (125 grams) when I need to convert from volume to weight, but your results may vary depending on the recipe you're using

*There seems to be some contention here. I'm from the US, where most people don't have kitchen scales (I'm the only one I know who does, despite being friends with lots of foodies). For us, measuring by volume is practically mandatory, and if I want to measure something by weight, I have to convert the measures myself since they're usually given as volume only. In other parts of the world, the situation is exactly the opposite -- everyone has scales, cups are nowhere to be found. Convenience is obviously relative.

senschen
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    I agree with all you say, except I think it's more convenient to measure by weight. There's really no downside. – GdD Jan 26 '18 at 12:43
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    @GdD Out of curiosity, where are you from? I'm from the US, and measuring by volume here isn't just convenient, its practically mandatory. Most people don't have kitchen scales, so they couldn't measure by weight if they wanted to. – senschen Jan 26 '18 at 12:46
  • I live in the UK now, but even before I moved here from the US I converted to grams because it's precision and easier. I've converted all my US recipe volume measurements to weight, writing the values in with a pencil. – GdD Jan 26 '18 at 13:02
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    @senschen At least in German kitchen, kitchen scales seem almost mandantory.. what we often lack is, actually, measuring cups! – Layna Jan 26 '18 at 13:47
  • @Layna That's true. I remember when I studied there I had to buy some, and I had a really hard time finding them. Its just different in different parts of the world-- some places measure by weight, some by volume. – senschen Jan 26 '18 at 14:21
  • Edited to address the conversation about convenience. – senschen Jan 26 '18 at 14:33
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    Well, to be precise, you need to know the required weight in the **recipe** . Otherwise, converting from a measured mass to the recipe's required volume only works if the person who wrote the recipe used properly sifted & shaken flour to begin with. – Carl Witthoft Jan 26 '18 at 15:37
  • @CarlWitthoft That's a problem with measuring flour by volume in general. If I don't sift and level my flour exactly like they guy who wrote the recipe I can still wind up with a different result. Different flours also measure differently, so there are all kinds of issues with converting flour volume to weight. OP didn't ask about those, though I did include a link to a pretty good overview. – senschen Jan 26 '18 at 15:47
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    When I was growing up (in the US) **no one** had a kitchen scale and there were two cookbooks that were pretty much the only ones people who cooked in the home used: *The Joy Of Cooking* and *The Betty Crocker Cookbook*. Both only had ingredients measured by volume, except meats. Things have changed a lot, but measuring flour by volume is still more common in a typical American recipe and kitchen than by weight. I do know a lot of home bakers (including my whole family) who do have kitchen scales, but I only in December started measuring flour by weight. – Todd Wilcox Jan 26 '18 at 16:59
  • @CarlWitthoft I suspect that an awful lot of recipes don't use sifted/shaken flour. King Arthur Flour suggests 4.5oz/cup (and I believe does sift) while a lot of other sources say 5oz/cup, and I've had a lot of luck using the latter as my initial guess. senschen, especially since this is the top/accepted answer, you could perhaps add a quick note about the fact that there's some uncertainty in the initial conversion? – Cascabel Jan 26 '18 at 19:24
  • @Jefromi note added, but feel free to edit if you think it needs more detail. – senschen Jan 27 '18 at 20:54
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In general, yes, you can absolutely weigh your flour (and other baking ingredients), and indeed should whenever possible.

There's an important caveat, however.

Weighing your ingredients produces more consistent results when reproducing a recipe. This is because measuring cups are not precision tools; there is variation in size from model to model. Bakers' techniques for filling them also vary. Indeed, the amount of flour can vary from scoop to scoop even for the same person.

When you weigh the ingredient, you eliminate two key variables: (primarily) the amount of air that ends up in the scoop, and the variations in size of measuring cups (grams don't change unless you change planets or your scale is broken). You also avoid simple differences in judgement of how full the scoop is.

Now, the caveat that emerges from this: when you make a recipe whose ingredients are measured by volume, you have to contend with this imprecision. The recipe writer's "1 cup" might be a cup minus a tablespoon by your measure. You've probably had the experience of a recipe coming out poorly the first time, and tweaking the ingredients next time. This is you compensating for the difference between the recipe author's equipment and technique and your own.

This problem does not go away if you switch directly to using weight. (In fact it might be exacerbated.) Since the recipe author did not give you weight, what was written down as "1 cup" might not be that standard 120g. It might be 128g, or 108g. While you are on the road to better reproducibility of the recipe, you likely still face a few rounds of trial and error.

jscs
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    I can not emphasize your last point enough... I use several websites that quote measurements both in cups and in ounces/grams and even they often disagree on what the equivalents are. One may say 4 oz and the other 4.5 oz per cup... there's no "standard" weight for a "cup" of anything. For example, King Arthur lists 4.25 oz = 1 cup and The Kitchn says 4.5 while Cook's Illustrated says 5 oz! – Catija Jan 26 '18 at 17:53
  • Except, perhaps, for a cup of water, at a specified temperature and pressure... – Dan Henderson Jan 26 '18 at 21:33
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    I have never in my life heard of the idea that a [measuring cup](https://www.amazon.com/Pyrex-Prepware-1-Cup-Measuring-Measurements/dp/B0000CFMZN) varies in size from model to model! That's why they have demarcations in ounces. Recipes that specify volume in cups always mean a measure that can exactly hold 8 fluid ounces. – tchrist Jan 28 '18 at 01:15
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    Except for the countries where the metric system is used, of course, and "1 cup" is likely to mean 250 cubic centimetres. – Dawood ibn Kareem Jan 28 '18 at 08:38
  • @tchrist From a quick check on amazon.com I found measurement cups using both legal and customary units as well as metric. And that was only on the handful that actually listed the weight, most were silent on the topic. And that's only the US, for extra fun just add Canadian cups to the mix. Ah imperial so much easier than SI units. – Voo Jan 29 '18 at 11:37
  • It's not intentional, and it's not a question of different units, it's simple imprecision in manufacture. – jscs Jan 29 '18 at 13:23
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You must measure the flour by weight to have any repeatable result. The more "technical" bakers (e.g., professionals, or also hobbyists who are into baking bread, where this really matters a lot) do this anyways. Also, using "cups" (i.e., volume) for everything seems to be a predominantly american thing, anyways, as far as I can tell.

Experiment: put flour in a jar, and ram it down with a big spoon. This will show you how much of its volume you can reduce, just by packing the grains of flour more tightly. I did this once when I had to store the amount contained in standard flour packages in a too-small container, and while I did not measure it, I'd say I got up to 25% less volume by ramming it down really hard.

AnoE
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    Instead of using a spoon, you may also try hitting the jar on the table a few times; the fill height will drop significantly (though not by 25%). See also https://en.wikipedia.org/wiki/Hausner_ratio (which is of even grater importance when "cooking" medicine) – Hagen von Eitzen Jan 26 '18 at 22:01