The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

understanding ounces--basic question

pietro79's picture

understanding ounces--basic question


I am Canadian, and would like to understand ounces.

There are fluid ounces for measuring volume, and avoirdupois ounces for measuring mass

So on this site for example, when recipes are posted in ounces, are all ingredients stated in ounces "ounces by weight" (avoirdupois), unless otherwise specified?




tjkoko's picture

Fluid ounce implies liquid measurement.  1 quart of water = 32 fl oz and it happens to weigh 2 lbs avoirdupoids.

1 oz avoirdupoids = 28.35 grams and used for measuring non-liquids.

2 oz of dihydrogen oxide (water in lay terms!) means 2 fl oz water and NOT 56g approx

2 oz sand means 56g approx and not 2 fl oz sand.


pietro79's picture

ok, so when i read a recipe that someone posts here, i'm to presume that...

16oz of stout beer is in fluid ounces

14oz of flour is in ounces by weight

4oz of molasses is... fluid ounces?

1.5oz of Sugar is...?

Would butter be fluid or weight?

How do you guys know?

Or in other words, what is considered a fluid?

obviously this measuring system predates the scientific revolution!



fancypantalons's picture

"ok, so when i read a recipe that someone posts here, i'm to presume that..."

Don't presume anything.  Just ask. :)  Depending on the baker, the liquids may be measured as weights, or as volumes... although, if they're using volumes, they should be given a stern talking to regarding bakers percentages. :)

louiscohen's picture

It is no accident that 32 fl oz of water weighs 32 oz.  One is defined by the other, ie, a fl oz is the volume of water that weighs 1 oz at some temperature (or maybe it's vice versa).  

fl oz and weight oz are the same for room temperature water, and anything else with the same density as water (which is a lot of stuff used in baking, eg milk; oil is pretty close, too).  

Of course not many solids have the same density as water (ice is slighty less dense than water).  Flour runs from 4 - 5 oz/cup, depending on the type of flour and how you scoop it; it weighs even less if you sift it.  So always weigh flour.

blaisepascal's picture

My assumption would be that if ingredients are listed in ounces, then they are avoirdupois ounces for measuring dry goods and fluid ounces for measuring liquids.  The main counter to that assumption would be if it were clear from the recipe that everything was measured in terms of mass or weight.  If there is one volumetric measure (cups of flour, teaspoons of salt, cups of water, etc) then I would assume that fluids measured in ounces are volumetric as well.



pietro79's picture

So if a recipe is stated only in ounces, I should presume all ingredients are expressed in ounces by weight? Even water?

For reference, I'm refering to this recipe:

PaddyL's picture

Butter would be weight in oz., as would flour, sugar, the dry ingredients, though I've occasionally seen sugar referred to as 'liquid'; just ignore that and think of sugar as weight in oz.  The liquids measured in oz., are fluid oz.  If you see, for example, 4 oz. butter, melted, then I'd weigh the butter (or slice it off as per the wrapper), then melt it and use it; don't think of it as a liquid.  That's what I do, and I'm also Canadian, and have been baking for years.

Yumarama's picture

Basically, anyway. A pound of butter is a weight, so 8 oz is a half pound, 4 ounces a quarter pound, etc, all weights. Until, that is, you get to three tablespoons of butter where things flip again since tablespoons are volume measures. 

It makes little sense. Then you have to start accounting for 16th of things.

But go by liquid or not liquid and you'll probably be fine.

flournwater's picture

You folks who are fortunate to have the metric system as a normal part of your every day life should count your blessings.  Americans repeatedly rejected the idea of converting to the metric system a number of times since I was a kid  -  looks like the majority here just don't get it.

I'd suggest you find a good conversion chart, convert all of the "American" recipe ingredients into something manageable (your system is perfect IMO) and forget about trying to figure out why we do what we do; we can't even figure it out so some of us just use a dip/level/pour method and hope for the best.

dghdctr's picture

I love the U.S., but I loathe our measuring system.

Cook's magazine did a comparison of different brands of measuring cups & measuring spoons, and the differences in the actual quantity measured were often significant.

So not only do we use a system based upon units of 16 (instead of units of 10), but we cling to habits of measuring those units with equipment that is not in standard agreement from brand to brand.

You can easily convert grams to kilos in your head, and you can often see the ingredient percentages without doing much calculation if the flour weight is expressed as a factor of "10".  Try that with ounces-to-pounds.

tjkoko's picture

dry good are measures in oz av

liquids are measured in measuring cups, fl oz.

4 years of chemistry, here, and THAT's standard within the field.  Such is why we need to convert to the metric system as the stupid English system is just that, plain confusing.

In the metric system:

dry goods are measured in grams (or kg)

wet goods measured in milliliters (or liters)

What's confusing in the English system is the term ounce: one cannot immmetidately determine if it's avoirdupoids or fluid.  Within the metric system it's apparent, grams versus milliliters.

MommaT's picture


I have had this problem very recently and researched it quite a bit.

Water's weight in fluid ounces is very close to its weight in avoirdupois ounces.  Unless you are dealing with very large volumes/weights, the difference is fairly inconsequential.  Obviously, if the density of the liquid is different (e.g., honey), then the weight/volume discrepancy will be greater.

I meticulously converted the fluid ounces in my Leader "Bread Alone" recipe to avoirdupois ounces to discover that I had to add back a large weight of flour to get the dough to its correct consistency.  When I use weight instead of volume to measure, it works out just fine.

Therefore, no matter what the recipe *says* one must still use your own judgement in the end.

Lastly, and much to my shock, I converted volume to mass and compared my 2 cup pyrex measuring jug to the properly converted weights.  Low and behold, it was 10% or more!  Caveat emptor!

My 2 cents worth...


Anna K's picture
Anna K
kellygirl's picture

What an excellent site.  Thanks Anna.

fancypantalons's picture

There's an important caveat, here.  While the other posters are right that ounces, when dealing with a liquid, are normally fluid ounces, that's *not the case with bread recipes*, at least artisnal recipes that are also expressed using bakers percentages... you know, the primary subject of this website. :)

When dealing with these kinds of recipes (ones expressed in weights and bakers percentages, like those in the BBA), if you see ounces anywhere, it's weight.  Period.  Fluid ounces are a measure of volume, and so they'd never be used in a bread recipe, which uses percentages and weights to express the amount for *all* ingredients, liquid or dry.

So if you're making bread, break out the scale, and measure *everything* with it.

flournwater's picture

I couldn't agree more.  I grew up cooking but did very little baking.  Until I discovered the bakers percentage system most of my baking ended in disappointment.  Given a recipe with only bakers percentages you don't need anything but a scale.  57% remains a constant, whether you're working with 100 grams of flour or 500 grams of flour.  IMO, there is no better method for preparing baked goods. 

tjkoko's picture

You are quite correct as far as bakers' percentages are concerned.  My oversight.

pietro79's picture

Yeah, I guess this is what I was subconsciously getting at.... I always see bread recipes expressed in grams for all ingredients... and so when I see them expressed in ounces across the board, I was feeling like they could all intend weight...

femlow's picture

"A pint's a pound the whole world 'round" is an old saying that actualy holds fairly true and is quite helpful for measuring most things when you aren't quite sure. So a pint (2 cups) of water is both 16 fluid ounces and 16 ounces by weight. It won't help with flour, but for all intents and purposes holds true for water, milk, butter, oil, molassas and syrups, even things like groud beef. Just thought it might help.

shakleford's picture

Just to further confuse things, an Imperial pint is 20 oz, so the saying for that measurement becomes "A pint of water's a pound and a quarter".  Not too important if you're using only American cookbooks, but if you have any old UK recipes, you may need to keep this in mind.

LindyD's picture

That old saying is cute, but it's a fallacy.

If we're looking for accuracy, a pint of water weighs 1.04375 pounds, or 16.7 ounces.

A pint of milk weighs 17 ounces and a pint of molasses or honey weighs 23 ounces.

Source:  "How Baking Works," by Paula Figoni.  You can find it in Google books.

femlow's picture

I didn't say it was perfect, just helpful. And if you are really trying for accuracy, things like molasses, honey and maple syrup can range "widely" (by your definition) in weight between one type and another, the weight of milk varies according to whether it is whole, skim, or somewhere in the middle, and if you are weighing something like flour, the weight is contingent on how much moisture is in it when you buy it, how it is stored, and depending on the latter, potentially how humid your home is. Even an "exact science" is not that exact and still relys on things like the bakers intuition regarding how the bread should look and feel.

tjkoko's picture

Judging by the number of posts made at this thread, it's become rather obvious what a waste of time the Imperial system of measurement is.

pietro79's picture

HAHAHA! At least this is true