How big is a cup? Flour volume vs flour weight

one cup of flourHow much does a cup of flour weigh?

Here’s a question that seems to pop up on a fairly regular basis in the bread forums. Someone sees a recipe that requires 3.5 cups of flour, or one that looks for 368g of flour. Either way, they’re used to the other method of measuring and they run into problems making the conversion from one to the other.

Why is it confusing? Because one is a volume measure and the other is a weight measure. As we all know a cup is not always a cup:  a cup of rocks and a cup of feathers will not weigh the same. Simply stated, volume and weight are not a consistent and easily interchangeable form of measure. Add in the confusion of liquid vs dry ounces and cups and you have a mess.

But there’s probably a set “standard” weight for flour, right? I mean, measuring flour is something people do ALL the time and have done for eons so someone, somewhere probably has The Definitive Weight for a “cup of flour”.

Well, the short answer is: No.

One reason for that is there are several different versions of “cups”. Not only do you have a liquid and dry cup – your glass Pyrex cup is for liquids, your plastic or metal scoop set is for dry ingredients – but there’s also regional differences between cups. A cup in the US is 8 fluid oz US but 8.32 fluid oz UK. 1 oz  UK  is .96 oz US. If we look at smaller measures, 1 tablespoon US is .5 oz but .52 oz UK. If you go with Australian measures a Tablespoon is different from either UK or US amounts.

Confused yet?

Even within the US, a cup (liquid) and a cup (dry) are different amounts; if we look at the volume measure of a dry cup it is 225 ml while a liquid cup is 237 ml. This is why you can’t accurately measure flour in a glass Pirex (liquid) cup. So the measure switches and can be confusing if the type of measure isn’t clear. Obviously, one may “assume” that if you’re measuring flour, you’d use dry volume and not liquid. But are you sure the recipe’s author didn’t just grab their glass Pirex cup to measure the flour? If it doesn’t specify, you might assume wrong. Now if you’re adding one cup of water and one cup of flour, the difference may be minor but when you get into several cups it may start seriously affecting your finished bread.

But let’s keep the discussion at converting flour from volume to weight (or weight to volume) and see how that works.

There are many sources for what one might hope is a “standard” for this conversion. You might think that with all the bread baking books out there, surely there’s a consensus within the professional baking stratosphere. You’d think anyway, right?

Again: Nope.

Here’s a brief rundown of what professional bakers use in their books, based only on the books I have in my personal collection. I’ve taken each author’s equivalence and, where they give (dry) oz but not grams, I’ve used a converter to get the missing info. It is internationally accepted that a US dry ounce (oz) is 28.349 grams.

Going from smallest to largest, all from professional US bakers:

  • Toba Garrett says 3.8 oz (107g)
  • King Arthur Flour says 4.25 oz (120g)
  • Peter Reinhart says 4.5 oz (127g)
  • Jeffrey Hamelman says 4.3 to 4.8 oz (122 – 136g)
  • Maggie Glazer says 4.8 oz (136g) – though to her credit she ALWAYS qualifies it as “About X cups…”
  • Rose Levy Beranbaum says 5.5 oz (156g)

And that’s just based on the books I happen to have. If your library is different or you hunt up a conversion table online, you’ll likely have various other amounts. According to one online converter I checked while writing this, 1 US cup of all purpose flour was 99g, even less than the above list.

So as you can see, there’s some wiggle room and certainly no “definitive” weight for a cup of flour. Even between the different flour manufacturers, their expected amounts vary. If you look at their nutrition labels, they’ll usually list their values per  “1/4 cup (30 grams)” or 33g or 28g or… It’s usually just on the bigger 20 kilo or 50 lb bags that you might see “per 100g”. But even then, not always.

And after you’ve put in “exactly” that much flour, you may still need to “adjust as necessary” anyway to compensate for your particular flour’s humidity and water absorption and to get the consistency the recipe wants (tacky, sticky, etc.). Different brands of “bread flour” are not all created equal.

So what’s a baker to do? Use digital scales and use recipes that specify weights, whether by dry ounces or grams. American cookbook publishers –  not necessarily the authors –  are notoriously reluctant to give up the volume measure for dry ingredients although many recent books are at least giving multiple measures, so if the author says “4 1/2 cups of flour” there will hopefully at least be an equivalent weight included in dry ounces and, with luck, grams as well, perhaps somewhere in the introduction section.

Also, keep in mind that many baker authors bake in large quantities so the recipes they use themselves are large and use big 20 kg bags of flour as a basis. So when they pass these recipes on to the book’s editor, they are the ones left to scale down the recipes to “home” sizes. And often enough, the editors (or even more likely their assistants) mess up the conversions. While the original recipe the baker author uses is tried and true and most likely in grams, what comes out in print can have a fair number of errors. In such cases, don’t blame the author and instead go by the larger volume amounts and scale down from that yourself. Chances are you’ll be more accurate this way.

For example, I have Jeffrey Hamelman’s book Bread: A Baker’s Book of Techniques and Recipes open here (I just made some Vermont Sourdough, p. 153) and his formula for this bread specifies, for the home size batch, “4.8 oz (1 cup)” of bread flour. In his Fougase with Olives recipe (p. 278) he gives 4.3 oz for 1 cup. Why the differences in the same book? Mr Hamelman rounds his cup amounts up or down to “closest” to weight simply for home bakers’ convenience; in other words, his posted cups are near the more precise weight amounts. The real recipe is in weights, the volume equivalents are best estimates. See page 90 for his explanation where he states, right at the start ” Cups and tablespoons are inherently inaccurate…”.

So according to the Yumarama Bread Blog, how big is a cup of flour? I presume 4.5 oz or 127 grams unless a specific weight is given in the recipe or elsewhere in the book. If I can, I’ll always try to go for a recipe that includes weights over one that uses only cups. And better still if it includes grams as they’re much easier to increase/decrease and, being smaller, are more accurate.

If I have a recipe that is given in ounces, but not grams (Hamelman’s BREAD [Home column] and Reinhart’s BBA for example don’t use gram weights) I have no problem whipping out the calculator and, using a conversion rate of 28.35 grams to the ounce, write the gram weight right in (in pencil – I’ve been known to get one or two wrong). So if, for example, the recipe calls for 11.8 ounces of flour, 11.8 X 28.35 = 334.52 so I’ll round that to 335 and enter it in the book. 1 lb 5.2 ounces is 21.2 (16 + 5.2) which in turn is 601.02 grams. Slowly, all the recipes will get upgraded.

So if you don’t own one already, go out and get yourself a good digital scale. It won’t cost a huge amount, probably in the $20 to $30 range for one with both ounces and grams (go for a minimum of 0.01 oz and 1 gram increments), a tare function and auto shut off to save battery life. Digital scales are available almost anywhere these days so do shop around and compare not just price but features.

A long auto-shut off timer is also helpful so your weight doesn’t vanish on you while you go grab that next ingredient. Many scales auto shut off after about 20 – 30 seconds of inactivity which I personally find a tad too short. If you can find a scale that shuts off after closer to 60 seconds, it will be much more convenient although such scales are a bit harder to locate. If you can’t, it’s still better to have one with a 30 second shut off than not have a scale at all.

What of smaller amounts like teaspoons? For those with a penchant towards miniscule accuracy, there are “Pocket Scales” that can measure down to 0.01 grams. Now that’s precision! For myself, I am of the opinion that when you get down to tiny amounts like 1/4 teaspoon of something in a 1500 gram ball of dough, extreme accuracy won’t really be noted in that scale. I have a set of good teaspoons – I checked them; not all teaspoons are accurate – and they will suffice for the time being. Until someone buys me a pocket scale, that is.

7 thoughts on “How big is a cup? Flour volume vs flour weight

  1. Frieda

    Thank you for this very informative post…I just got asked that very same question today. In teaching my bread classes, people want exact amounts and a scale is the way to go. I just purchased a Salter digital scale for $20 at the local Ross store, which I am very satisfied with. Weights, like you said, are a good way to start the recipe ~ then adjust according to atmospheric conditions and type of flour.

    Reply
  2. Chris

    Thank you for digging into this! I had noticed the discrepancy in some of the same books. I’m working on a cookbook and plan to list ingredients in grams and cups. I sometimes wonder how much push back I’ll get from a future publisher.

    Then, there’s also the difference in weight between whole wheat flour and bread flour and no apparent agreement on that either!

    Reply
    1. Paul Post author

      @Chris: This is in no way presented as “in depth” research, just me gleaning and figuring stuff based on a quick perusal of what info I have at hand. So in effect, one can take my results and add them to the list of inconsistent measures for a cup of bread flour.

      Go on the internet and look up tables of ‘standard kitchen ingredient weights’ (and there are several) and you’ll see they’re all over the place too. I’d expect this is too ‘fluid’ an ingredient to pin down. Different flours from different manufacturers from different regions, even if they are all labelled “Bread Flour” are going to vary, although a 50% variance may be a little much. The final aim is most usually the dough consistency so even if everyone was OK saying “1 cup = X oz or Y grams” the baker standing in their own kitchen using their specific flour still needs to “adjust as necessary”.

      But it would still be nice to have a set base amount everyone is OK with as useful for most everyone everywhere. Seeing weights ranging anywhere from 3.8 oz to 5.5 oz is just flat out confusing.

      As for your book publisher balking, I can’t see the logic. It’s easy enough to include three values , cups, oz and grams or preferably grams, oz and cups, thereby relegating volumes to a “third choice” status. Yes, that would be a bit of a psychological game. I might even go with something similar to Maggie Glezer’s take:

      “Bread flour: 350 gr, 12.3 oz, about 2.75 cups” (my bold)

      where she makes a point of the volume amount being approximate in every recipe she includes.

      Just let the reader pick which version they prefer. Then, adding short explanation in the intro for the use of all three measures and a statement of what you assumed a cup weighed should suffice.

      And yes, different flour types like whole wheat, rye, etc. are a whole ‘nuther ball of wax. Another reason to ditch volumes and simply go with weight.

      Although it’s a fact that there’s a great reluctance in the US to change off the volume system despite it’s clear shortcomings, this shouldn’t preclude the promotion of a better one. Just as a large swath of people won’t buy a recipe book without cups, many bakers would skip over one without weights.

      Good luck with the book, BTW!

      Reply
  3. Rita

    Very much appreciate you writing this wonderfully detailed article. Help me a good bit however it still leaves me confused as to how best to calculate weights in bread. I am new to bread making and currently use a bread maker which is a very poor way to make bread: I am trying to get up the courage to leave the bread maker behind and just make great bread without the crutch…. Thanks again for your help!!!

    Reply
    1. Paul Post author

      Hi Rita,
      I am happy to see you are looking to switch away from volume to weight measures and also to step up from bread machine to hand made (that’s “Artisan”!) breads. Note that these are two different endeavours and you don’t need to tackle both at the same time if you are feeling a little overwhelmed by the prospect.

      You may find this conversion chart I’ve made of standard baking ingredients helpful when needing to see how many grams of “X” is in a tablespoon, etc..
      Visit the and print out a copy to keep with your baking literature.

      I recently had a friend visiting who wanted to get into bread making and was putting it off because she did not have a stand mixer (i.e. a KitchenAid or CuisineArt mixer). I showed her how to make bread without using these (albeit useful but not mandatory) machines by using the Stretch & Fold technique. She has since made a few beautiful loaves on her own with the only appliance needed being the oven and an instant read thermometer. Remember that people were making bread for thousands and thousands of years before bread machines and electric mixers were ever invented. You can do it to, and without even having to spend ages kneading the dough by hand.

      Check out the links above and see if they help you out! If you need any help, just post a new comment and I’ll do whatever I can.

      Baking By Hand Book CoverAnd don’t forget that I’m giving away a copy of the book “Baking by Hand” (see the post here) that details, well, how to make bread and pastries without the need of an electric mixer. I would suggest popping your name into this draw and maybe you’ll be the lucky winner! The giveaway is running until Nov 25, 2013. Don’t tarry too long!

      Happy bread baking!

      Reply

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