Talk:Fluid ounce

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Utter Nonsense![edit]

Ounces are most commonly mass. The ounce-force exists but is rarely used.

When some one steps on a bathroom scale, they are measuring weight, in pounds and ounces. When a newborn baby is weighed it is weighed not "massed" and the weight is measured in pounds and ounces. When someone puts a letter on a postal scale it's weight is measured in ounces. These scales and all commonly used scales are incapable of measuring mass, they can only measure weight. Even a balance type scale cannot measure mass directly, it can only infer it from the relative weight of two objects.

I don't know what planet you're from, but on earth ounce is a measurement of weight, not mass! John Alan ElsonWF6I A.P.O.I. 00:11, 18 December 2014 (UTC)

I'm from a planet where a pound is defined as 0.45359237 kilograms.[1][2][3][4] When I stand on a set of bathrooms scales, sure I'm measuring weight but the reading is in kilograms not newtons. Of course, if I were on another planet, this wouldn't give me the correct mass, but the fact that these scales don't have the warning "for use on Earth only" doesn't seem to worry me very much. Okay, it's true that scales can only measure weigh and that mass is then inferred and it's true that we speak of weighing things not massing them but that doesn't make the kilogram a unit of mass, which, by the argument presented here, it would be. The kilogram is not a unit of force, nor therefore is the pound nor the ounce (as the pound is defined in terms of the kilogram and the ounce in terms of the pound). They are all units of mass. Jimp 04:35, 18 December 2014 (UTC)

No, the only time the ounce it a measure of mass is when someone does a metric conversion which is technically wrong, since the ounce is a measure of weight and a kilogram is actually a measurement of mass. The ounce is and always has been a measure of weight. The conversion of kilograms to pounds and ounces is only correct under normal gravity.

If a fat man stepped on a bathroom scale on earth it would say he weighed 300 pounds. On the moon it would say he weighed 50 pounds. In both cases it would be correct because though his mass would be the same his weight would be different, and pounds, like ounces are a measure of weight, not mass! John Alan ElsonWF6I A.P.O.I. 05:00, 18 December 2014 (UTC)

Please consult the legislation of the United States, the United Kingdom, Canada, and other countries where the pound and ounce are legally defined. They all say 1 lb = 0.45359237 kg. No gravitational fields or location is mentioned. This equation is valid everywhere. If a kilogram is a unit of mass, so is a pound, and so is an ounce. Some of the confusion has to do with the word weight which is ambiguous. Some textbooks and physics teachers insist that weight can mean only "force due to gravity," but nobody can control the English language. Like it or not, weight can and usually does mean "mass." Indefatigable (talk) 19:27, 18 December 2014 (UTC)

Clean up[edit]

I don't like trashing decent articles with an template, so for minor fiddles like this, the clean template above makes more sense.

  • I've been away south helping out with the post H. Katrina recovery, so I'm not up on a lot of the newer changes, like footnotes, or I'd do this myself. I've got about 3-4 more edit pages to pop off and finish in a string and being after midnight, I'm not going to research such now!
  • The need I see is to move the legal cites down into the nice new footnotes.

Kill the clean w/o asking.FrankB 06:00, 20 March 2006 (UTC)

Yeah, it's a mess ... still. Jɪmp 08:34, 18 December 2007 (UTC)
It's somewhat tidyer now. Jɪmp 19:12, 18 December 2007 (UTC)

(Fluid) ounce[edit]

It is infuriating the number of recipes that, due to the laziness of the writer or copier, fail to include the word "fluid" and yet it is implied with the item to be measured. Since when would you measure out 6 ounces of water? Or pizza sauce? Sometimes, it could be either weight or volume, but the frequent omission of the word "fluid" leaves it ambiguous.

This is one reason why I disdain the customary/imperial measures and prefer metric. At least there's no such thing as a "fluid gram" or a "mass/weight millilitre"!

Fl oz is no harder to print than ounce(s). GBC 03:10, 13 November 2006 (UTC)

Well, in metric it's not customary to volumes by weight but measures of density are used.GreatMizuti 14:23, 23 December 2006 (UTC)

"Since when would you measure out 6 ounces of water? ": since I was a child. I frequently measure out a particular number of ounces of water. And, what's more, I'll tell you how I do it: I pour water into a measuring cylinder marked in fluid ounces up to the "6" mark. Of course this would theoretically be accurate only if I checked the temperature and looked up the density at that temperature, but the difference is far too tiny to matter for domestic purposes. As for pizza sauce, if I were to use ready-made pizza sauce, and if I were to think that a measurement in a recipe for a pizza were critical enough to be worth the trouble, rather than just being a rough guide, I would weigh it, if the recipe gave a number of ounces. Why wouldn't one? I don't see the problem. (talk) 16:57, 16 February 2009 (UTC)

If you are measuring a fluid, use fluid ounces. What's so difficult about that, GBC? ~ MD Otley (talk) 15:21, 9 May 2009 (UTC)

He's got a point. For example, I have here a recipe that calls for three ounces of sugar. So which do I use? Granulated sugar is both dry and fluid, so it could be either dry or fluid ounces. Rees11 (talk) 17:44, 3 September 2009 (UTC)

Ah, no. Granulated sugar is dry. ~ MD Otley (talk) 03:20, 4 November 2009 (UTC)
I guess sugar is dry in the sense that it's dry to the touch, but it's still common to measure it in units of volume. For instance, when I cook rice, I measure it in cups, then add twice as much water. It even says to do so on the back of the package. Outside the US, deciliters (dl) are common for rice, sugar etc. So yes, I definitely see the problem; I don't think it's always clear whether to measure volume or mass, and 10 fl oz of sugar is very different from 10 oz of sugar. A sentence like "add 3 ounces of sugar and 6 ounces of water" would definitely confuse me. (talk) 22:15, 29 November 2009 (UTC)

I know this is a rather old discussion, but the reason there is rarely ambiguity is that we americans seldom use scales in the kitchen, and nearly all ingredients are measured by volume, usually cups. (talk) 12:32, 7 February 2011 (UTC)

As the main said, no recipe would ever say to use a certain number of ounces of sugar: sugar measurements are in teaspoons, tablespoons, or cups. The same goes for other ingredients made up of many small pieces, like spices, flour, and loose grains. Liquids use the same volume measures, but can also use fluid ounces, although that's not as common as fractions of a cup. ~ MD Otley (talk) 19:15, 13 September 2015 (UTC)


1 US fluid ounce is exactly 29.5735295625 ml. You can derive this from the following exact measures:

  • 128 fluid oz = 1 gal = 231 inch^3
  • 1 inch^3 = 16.387064 ml

Source: [5]Rees11 (talk) 23:35, 8 April 2010 (UTC)

What would it be like if, we here in the United States used the British Imperial fluid ounce (28.4 ml), the British Imperial cup (284 ml), the British Imperial pint (568 ml), the British Imperial quart (1.136 litres), and the British Imperial gallon (4.544 liters)? —Preceding unsigned comment added by Harvey994 (talkcontribs) 18:54, 18 June 2010 (UTC)

For one thing, gasoline would suddenly seem to have gone up by 20% Moletrouser (talk) 13:01, 6 February 2011 (UTC)

The article's explanation of origins of gallons says ".... Thus, the mass of an imperial fluid ounce of water is one avoirdupois ounce (28.4 g) The US ounce is based on the earlier definition of one gallon equalling 231 cubic inches. This measurement at first glance does not seem to have any tie to mass, however it is believed[by whom?] to have come from a previous measure of a gallon as being 224 cubic inches (just 7 cubic inches less, both numbers being multiples of 7) which was used because it was the exact volume of 8 pounds of wine.[1] Thus one pint of a wine gallon is equal to the volume of one pound of wine, and there are 16 fluid ounces in a pint, just as there are 16 ounces in a pound." Some problems: (1) explaining a difference by describing an origin that differs from the present case in _two_ respects (224 vs. 231, _and_ water vs. wine) does not let the reader sort out what's due to what. And the concluding "thus" about being different by about four percent does not follow from the information presented. (2) The 224-cubic-inch wine gallon description that this passage attributes to Reference 1 is not to be found in Reference 1. What is to be found there is different: says that it's the _231_-_cubic_-_inch gallon (not the 224) that is the Old English Wine Gallon, and reports the idea that it was chosen to be the volume of 8 pounds of wine in _troy_weight_, not avoirdupois. (3) This passage would be a lot more helpful if it got around to saying how many pounds a US gallon does weigh. Archaeopterix (talk) 17:28, 5 July 2012 (UTC)

Agreed that paragraph is a mess. I'm familiar with the subject and read it three times and still don't know what it's trying to say. Does someone want to try fixing it? I'd fix it myself, but I'm afraid my fix would be to just remove the whole thing. Kendall-K1 (talk) 17:04, 20 September 2012 (UTC)
I'll see what I can do. Zyxwv99 (talk) 03:30, 21 September 2012 (UTC)
I'm going to put in some unreferenced material this morning, just because I'm in a hurry. Last night I studied the main reference I intend to use: Connor and Simpson's Weights and Measures in Scotland which has plenty of information about England as well. The relevant material is around pages 153 and 231 (plus nearby pages) in chapters 4 and 6. There are also some good references in related articles. Zyxwv99 (talk) 12:33, 21 September 2012 (UTC)
That's better, keep going! This is confusing: "The US ounce is based on the earlier definition of one gallon equalling 231 cubic inches." I assume this refers to the US gallon being based on the UK wine gallon, but "earlier" is confusing because the US gallon is still 231 cubic inches. I would just take out the last sentence starting with "This measurement at first glance does not seem..." unless you can figure out what it's trying to say and clarify it. Kendall-K1 (talk) 18:00, 21 September 2012 (UTC)
I'll try to straighten this out tomorrow. Whoever wrote that almost knew what they were talking about. The US gallon of 231 cubic inches is based on the Queen Anne wine gallon, which in 1706 was given two slightly conflicting definitions: 231 "cubical inches" and a second definition about the size and shape of a cylindrical container that would be absolutely correct if pi were equal to 22/7. The Queen Anne wine gallon was actually in use since the 1500s. I forget the details (need to look it up) but it was originally something like 233 cubic inches, based on a pound of 15 ounces avoirdupois, the pound being either Flemish or Florentine, I forget. (At the time, England was still a relatively poor country, while Paris, Flanders and Florence were rich and major trading partners.)
The part about the gallon of 224 cubic inches is not really right. That'a a whole different gallon, the Guildhall gallon (the oldest gallon in English history), originally a 9-pound gallon where each pound was 15 Paris troy ounces of 472.5 modern grains (of 0.06479891 gram, minus 0.1 percent for the Carysfort Committee error of 1758). Zyxwv99 (talk) 03:28, 22 September 2012 (UTC)

When did Floral Ounce become Fluid Ounce?[edit]

I am in my 30's. I was raised always using Floral Ounces. Now everyone uses Fluid Ounces. When did this change happen? Presidentbalut (talk) 20:28, 20 January 2014 (UTC)


There is nothing how-to manual-ish about defining fluid ounces in terms of metric measure. It is how the articles on the international yard and pound, pint and gallon defines those units. The current definition is circular and fails to give the reader a quick reference point to the similarity and difference between the units by reference to a independent yard stick (so to speak). Moreover both US and Imperial fluid ounces are legally defined in terms of metric measure. — Blue-Haired Lawyer t 14:42, 20 August 2014 (UTC)

30 ml ounce used for medical labelling?[edit]

I don't think this is true. Here is a counter-example: [6]. Note the label, "4 FL OZ (118 ml)". Kendall-K1 (talk) 15:23, 15 September 2016 (UTC)

I agree that that is consistent with using an avoirdupois ounce. However, on the same page, the next label shows 1 teaspoon = 5 ml, which would imply that 1 fluid ounce = 6 teaspoons = 30 ml. Furthermore, California says] that a fluid ounce is 30 ml when measuring liquid medicine. Unfortunately, those could be rounding from 1 tsp = 4.9289216 ml or 1 fluid ounce = 29.57353 ml. 𝕃eegrc (talk) 18:21, 15 September 2016 (UTC)
Motrin Children's Ibuprofen Oral Suspension, Original Berry Flavor, 4 fl oz (120 ml) is instead consistent with the US food labelling fluid ounce. Also see Allegra Allergy, Children's, Non-Drowsy, Berry Flavor, 4 fl oz (120 ml). 𝕃eegrc (talk) 18:33, 15 September 2016 (UTC)
Also take a look at, modium A-D Anti-Diarrheal, Mint Flavor, 8 fl oz (240 ml) and Tylenol Cold & Flu, Severe, Warming Liquid, Honey Lemon, 8 fl oz (240 ml). To see more, try a Google search for, for example, "8 fl oz (240 ml)" (with the quotes).
It seems that we have found contradictory examples. Perhaps change the article text to say something like "It is sometimes used in medical labelling". 𝕃eegrc (talk) 18:39, 15 September 2016 (UTC)
I would not want to use any of these labels as a source. The California Pharmacy flyer would be acceptable with attribution. (Kind of funny how it starts out "It's important to measure ... accurately" then proceeds to give the wrong size for a liquid ounce. I suspect they just rounded up.) Kendall-K1 (talk) 23:04, 15 September 2016 (UTC)