© Denzil Green
A Measuring Cup is a demarcated vessel used to measure liquid ingredients. In the UK, they are delineated in pints and ounces, and in metric. In North America, they are delineated in cups and ounces, and in metric. In the rest of the world, they are delineated in metric.
North America confuses the rest of the world by also using Measuring Cups to measure dry ingredients in addition to liquid ingredients.
One of the difficulties in measuring with cups is that "cups" isn't a term of commerce. Items that are measured in North American kitchens by volume using cups, such as sugar, butter and flour, are actually sold by weight. A pound of flour is always a pound of flour, whether sifted or not, but this is not so for a cup of flour. If you take a cup of flour and sift it and put it back in the cup, you will now have more than a cup of flour because the added air in the flour will have increased the volume of it. Another example is a cup of walnuts: whole, halved, chopped, and ground will all yield a different weight of walnuts.
In an attempt to control this possible disparity, recipe writers will often attempt to describe precisely how they want you to put the ingredient in the cup by using adjectives such as generous, loosely-packed, tightly-packed, scant, rounded, heaping, sifted, level, etc.
Coffee machine makers seem now to refer to a cup as something that must be a 100 or 125 ml (3 or 4 oz) cup. Their cup measurement doesn't match up with any kitchen Measuring Cup, let alone any coffee cups or mugs that anybody actually uses to drink out of. But they can do that, as cup is not a legally defined term.
Dry Measuring CupsIn North America, there are cups for dry measure and cups for liquid measure. Most cooking instructors direct you to buy both. In truth, Measuring Cups are hardly ever labelled as such in the stores, perhaps because few outside of Home Economics instructor circles really know the difference. If you did manage to find some with packaging clearly labelled as one or the other, unless you knew the difference to look for you, you wouldn't be able to remember which was which after you got the packaging off.
The single difference between wet and dry cups are the rims. Liquid ones have a pour spout on them, dry ones don't. Dry Measuring Cups are meant to be filled right up to their rim. They generally look like large measuring spoon sets. They have straight sides, flat narrow rims and flat bottoms. The idea is that you take a knife and whoosh it across the top to level it off. Good ones have the measurement both on the handle, and on the back, so that if you hang them up, you can easily see the measurement on the back for quick access.
Dry Measuring Cups are easy to use as scoops straight in the flour bin, etc. Some put very long handles on them for just this purpose, so that your knuckles don't end up dusted in flour. But if the handles are too heavy, they won't sit level on a counter -- the heavy handles just tip the flat bottoms over. Be careful, though, using metal ones to scoop up stuff like hard butter, etc: the handles tend to bend easily.
Dry Measuring Cups are actually technically liquid measures -- they measure in volume. 1 cup of water from them will be 8 oz, just as in a liquid cup. There is no official "dry cup" -- there couldn't be, as dry varies so much depending on what you are weighing: rice, macaroni and flour don't fit into the cup in the same way, so it's only the volume that is measured, not the actual quantity in weight.
In practice, most people just use what they have as a Dry Measuring Cup, which tends to be a liquid one. You put in the flour, shake it then eyeball it -- as generations of Americans and Canadians have now done.
Dry Measuring Cups come in sets of 1/4/, 1/3/, 1/2 and 1 cup; odd-size Dry Measuring Cups are 2/3 cup, 3/4 cup and 1 1/2 cups. They are made in plastic and metal.
Liquid Measuring CupsLiquid Measuring Cups have a pour spout on them, which dry ones don't. Many will have enclosed handles so that the cup can be hung from hooks. Pyrex ones always used to have such a handle, but for some reason around 2000 or so they started putting out more cramped handles that are open at one end, and so they can't hang on a cup hook.
They are generally made of glass or plastic, with glass being more usual. Either will have the measurements marked off at the sides. Most glass ones are made of a heat-resistant glass such as Pyrex. Transparent plastic ones can cloud over with time, making it harder to see clearly how close the liquid you are measuring is matching up to the marks.
To accurately measure liquids, you have to raise a Measuring Cup to eye level or crouch down to its level on the counter. The top measurement line (1 cup, 2 cups, etc.) is always a bit down from the rim, so that when you need to measure the full amount, it won't spill over the edges.
Very large liquid Measuring Cups can double as mixing bowls.
Some Measuring Cups are designed as "sliding bars." You move the handle, which in turn moves a dividing compartment in the cup portion, to decrease or increase the volume of the area available to hold ingredients.
Adjustable Measuring Cup
Adjustable Measuring Cup
© Denzil Green
Another novel design is that of a plastic cylinder fitting snugly around a sliding tube. Called a "Measure-All® Cup", a "Push Up Cup" or a "Wonder Cup" (yes, it is starting to sound like something else, isn't it?), you push the tube up or down inside the cylinder to the right measurement line you want, then fill. As you add ingredients, you raise the tube to line the measuring lines up with what you have already put in, and then measure the next ingredient in. In this way, it works a bit along the same principle of an adjustable electronic weigh scale. This design is used for solids, or semi-liquids like honey or mustard, but not liquids. They are particularly handy for ingredients like jam, peanut butter or butter that can be hard to get out of measuring cups: you just push the tube up, forcing the ingredient out of the top.
AccessibilityA few Measuring Cups, such as those designed by OXO, are now designed in such a way that looking on them from overhead will give an accurate measure. This means you don't have to crouch down to counter height.
These cups are actually divided in two by a slanting piece of plastic, with the half behind the plastic shut off, out of use, and on the slanted divider inside are the measurements, though measurements also on the outside. Some people feel, though, that the angles created inside the cup make it hard to scrape ingredients out.
Most measuring cups are designed for right-handed people.
Some measuring cups for those who are blind or have impaired vision have raised measuring lines on the insides of the cups, so you can feel where what you are measuring is at.
Displacement MethodThis is a method for measuring solid, "water proof" ingredients such as shortening, lard or butter that is taught in home economics classes. It is considered more accurate than trying to pack it in, then scrape it out, but it is more work.
Using this method, if the measurement needed were 1/2 cup shortening and you have a 1 cup capacity Measuring Cup, you would fill the cup 1/2 full of cold water and add shortening. When the water reaches the 1 cup mark, you have added 1/2 cup of shortening. You pour off the water and the 1/2 cup shortening remains.
Alternatively, shortening may be placed on the kitchen table until it softens enough to pack it accurately in the cup, or, you can pack harder shortening or butter into the cup tablespoon by tablespoon to avoid leaving large air gaps.
UK CupsAmerica calls its measuring system "English", but the truth is, contemporary Brits tend to measure dry or solid ingredients by weight, not volume.
Brits do, though, use measuring cups for liquids. But they tend to call them "measuring jugs", and they tend to be delineated in pints, not cups. Brits relate to "pints" (British pints of course, being 20 oz as opposed to 16 oz in the USA), and where North Americans might say "1 cup" (8 oz), Brits will say "1/2 pint" (10 oz), with the rest of the recipe being scaled accordingly, naturally. But, outside of home canning, North Americans are losing an everyday understanding of what a pint is (as well as yards, for that matter.)
Consequently, North Americans and Brits are probably better off using metric as a common language.
An American cup is 250 ml, an American 1/2 pint is 25 0ml, a British 1/2 pint is 300 ml. If you're a North American working with a British recipe and you see 1/2 pint, measure 10 oz (300 ml.) If you're a Brit working with a North American recipe and you see 1 cup, measure 8 oz (250 ml) in volume.
You can figure on a standard 1 cup measuring cup as being 250 ml in the United States, Canada, New Zealand and Australia.
All that being said, with all the recipes that are now flooding across the pond from North America, as well as from Australia and New Zealand, Brits are exposed now to a great many recipes calling for volume measurements of solid ingredients.
In response to the need created by these recipes, you can now buy sets of measuring cups now in stores such as Tesco's that are approaching the North American measurements for a cup. On them you see marked 1/4 cup (60 ml - Ed.: close enough), 1/3 cup (80 ml), 1/2 cup (125 ml), 1 cup (250 ml.) Nigella Lawson sells measuring cups in the exact same dimensions, shaped like tea cups, with the level line marked inside beneath the rim. Some, though, have noted that their lack of spout makes them hard to pour liquids out of, and having the level line beneath the rim makes them hard to level off dry ingredients with.
In the UK, many bread machines are shipped with cups for measuring flour, but there it is very hard otherwise to find such measuring cups for levelling off at the top, even though bread maker machine instructions there will tell you to do so.
Brits who want to cook a lot of North American recipes are probably best to grab somehow a set of North American measuring cups.
Breakfast cups for measurement in BritainInformally, some older British home cooks used to refer to a "breakfast cup" for volume measurements of solids. You may see an older, home recipe call for a breakfast cup of flour.
Mid-1900s British recipe using measurement in cups. Note though that the butter is still weighed.
© Calum Rogers
Some define this as being 10 oz in volume, half a British pint. Others wonder if the breakfast cup meant really was that large and suggest that it might have been a tea cup instead.
Nigel Slater says in response to a reader's question, "Q: When an old but very efficient recipe says to use a breakfast cup, what are the correct dry and liquid measurements to use in this modern age? A: A breakfast cup was the sort you might use for a large milky coffee. The measurements are very much equal to an American measuring cup. So for any recipe specifying a breakfast cup you should allow 200 ml for a full one. Obviously with dry measures it will depend what you fill it with." 
Note that even Nigel Slater is uncertain about cups, implying that an American measuring cup is 200 ml (it's usually metrified to 250 ml). So it's uncertain if Slater intended to mean a full cup (8 oz / 250 ml), or actually meant 3/4 cup (6 oz / 175 ml) or possibly 7 oz (207 ml).
Measuring Cups in Other CountriesIn Japan, a modern cup for kitchen measurements is 200 ml. There is also a traditional Japanese cup, called a "go", which is about 180 ml. A "go" was used for purposes such as measuring rice, and sake. Sake bottles are 720 ml, which is four "go" 's of sake (4 x 180 ml.)
Some Mexican recipes still are given in cups (called "Taza"), as in "¼ de Taza de Leche" (1/4 cup of milk.) Dry ingredients may even be given by Mexican recipes in cups.
Cups are also used for cooking in Australia. North American and Australian cups are the same size: 8 oz / 250 ml.
Metric Measuring CupsSome metric enthusiasts (usually scientists in English-speaking countries), with the zeal of converts or former smokers, charge like Don Quixote at anyone who talks about "metric cups" or "metric teaspoons" saying that they don't exist; you'll never see such a measure in labs that use metric.
While it is true that current humanistic thinking holds that whatever can't be seen in a lab doesn't exist, the plain fact is that home cooks blow this thinking out of the water when it comes to metric Measuring Cups. They have them, and use them.
Even in metric countries, cooks at home often use cups for dry measure. Some Measuring Cups in Italy, for instance, have ml for liquid on one side, and g (grams) on the other for measuring the weight of flour based on its volume. Elsewhere in Europe, measuring cups often give ml measurements on one side, and various g equivalent marks for flour, rice, sugar, etc on the other side.
And two quotes from Australian government officials show that they certainly believe that a metric Measuring Cup exists:
- "A ‘cup’ is a standard metric cup (250 mL.)" 
- "The vast majority of data in this File comes from the original US Codebook files adjusted to metric measures, for example, US cup to metric cup. " 
 Lester, Ian H. Australia's Food & Nutrition. Canberra, Australia: Australian Institute of Health and Welfare. Australian Government Publishing Service.
Appendix D, Page 312. 1994.
 Introduction to AUSTRALIAN FOOD AND NUTRIENT DATABASE ( AUSNUT 1999 )
If you have a scale, you can check to see how accurate your measuring cup is. On the scale, weigh out 1/2 pound of water. Pour into your Measuring Cup. The measuring cup should show exactly 1 cup / 8 oz.
 Slater, Nigel. Ask Nigel. Manchester: The Guardian. 24 May 2009. Accessed August 2015 at http://www.theguardian.com/lifeandstyle/2009/may/24/ask-nigel-slater-cooking-tips
Measuring ToolsCuillerée; Jiggers; Measuring Cups; Measuring Spoons; Pony; Pugnetto; Scales
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Verre gradué (French); Taza para media (Spanish); Recipiente graduado para cozinha (Portuguese)