The Delightful Diversity of "Cup" Sizes in UK/US/AU/NZ Cooking

Volumetric measurements (using the volume of a container) are inferior to Gravimetric measurements (i.e. weight) in most ways. Weighing is faster (for a given pareto-optimal degree of accuracy), can achieve greater accuracy, and most importantly there will be less dishes to clean up afterwards.

Most irritatingly, "cups" and "spoons" mean different amounts in different countries. Even worse, sometimes three "thirds" of a cup are less than one cup...

[Updated 2020-03-22: Added cup densities for wheat bran and oat bran]

Cups

I can understand the volume of a standard "cup" being different in different countries, but surely that's a good reason to specify recipes in a standardized unit (i.e. litres, or millilitres). The US cup size is 240ml rather than the 250ml used in Australia, New Zealand and Canada. 4% difference is usually OK.

The 225ml cup size used in British/UK cooking is often not OK, at 10% difference it is more likely to break delicate recipes, such as pastries. Japanese "cups" are worse at 200ml, and some countries use "cups" as small as 150 or as large as 280.

On the upside, it seems to be more common in modern European recipes to use weight measurements instead, possibly as a result of the above international cup confusion.

Country AU/NZ/CA US UK
1 cup 250 240 225
3/4 cup 190 180 170
2/3 cup 170 160 150
1/2 cup 125 120 110
1/3 cup 80 80 75
1/4 cup 60 60 55

Fractional Cup Catastrophes

As you can see from the above table, an AU cup is 250ml, but an AU 1/3 cup measure is 80ml. A third of 250 is 83⅓, but to "simplify" things a third of a cup has been quantized to 80ml in Australia.

This results in the "simple" confusion that three 1/3 cup measures are slightly less than a single 1 cup measure.

Cups of Common Ingredients

For reference, this table contains the weight of 1 Australian or US cup of common ingredients rounded to the nearest 5g, plus the density for fine grained conversions.

Ingredients 1 AU Cup (g) 1 US Cup (g) Density (g/ml)
Honey / Golden Syrup 350 335 1.4
Water / Milk / Eggs 250 240 1
Butter / Margarine 225 215 0.9
Caster Sugar 200 190 0.8
Brown Sugar / Icing Sugar 150 145 0.6
Fine Wheat Flour / Cornflour 125 120 0.5
Oat Bran 100 95 0.40
Rolled Oats / Cocoa / Coconut 90 85 0.35
Wheat Bran 55 50 0.22

That's not a Spoon, This is a Spoon

Although everyone seems to have standardized on a Teaspoon being 5ml - and a Dessertspoon being two of those - Australia has decided to break with everybody else by defining a Tablespoon as 4 teaspoons, whereas in other countries it is 3 teaspoons.

Obviously with the AU tablespoon being 133% of the US/UK teaspoon, there is a huge potential to mess up recipes. This is particularly bad considering that spoon-sized measurements are usually used for salt, baking powder and flavourings - using the wrong nationality of spoon can cause a recipe to fail to rise, be unpleasantly bitter or salty or otherwise imbalanced.

Country AU UK/CA/NZ/US
Teaspoon 5 5
Dessert spoon 10 10
Tablespoon 20 15

The capacity of non-measuring spoons (i.e. the teaspoons and dessert spoons in a cutlery drawer) usually bears no relation to the measurement spoons. Cutlery spoons vary widely in capacity depending on the style.

Ounces and Pounds

Ounces and Pounds have had centuries of confused definitions. Apart from regional variations, there are different types of ounces and pounds for different materials, such as the Troy ounces/pounds used to weigh precious metals and the fluid ounce as a volumetric measure of liquid.

Even worse, the fluid ounces used for volumes are derived from different base materials in different countries. The traditional English ounce is derived from the volume of one (weight) ounce of wine, whereas in Scotland the traditional fluid ounce is derived from the volume of one ounce of water. In 1824 the British government redefined its systems of measurement to base its imperial units on the weight of water; however the US imperial units are still based on the Wine gallon. The US fluid ounce is thus 4% larger than the British fluid ounce.

Jigger - the Vaguest Term of All

It can be anywhere between 20 to 50ml and it's only use is as an antonym for the word "specific".

Even the word "Jigger" has dozens of other meanings apart from as a unit of measurement - it is also a type of fishing lure, several types of machines used in fishing, pottery, dyeing fabric and cargo handling, a small fishing boat, the inner button on a double-breasted coat, a synonym of penis, a synonym of vagina, the name of at least two towns, and an ethnic slur. Avoid unless your goal is achieving maximum ambiguity.