The metric tablespoon and the changing size of a spoonful
Three teaspoons fill a metric tablespoon, except in Australia, where the measure takes four. Behind that small difference lies a history of kitchen volumes that share familiar names while holding different amounts. In Britain, Canada, and New Zealand, the tablespoon under the metric system has become more or less standardized at 15 milliliters. In Australia, the tablespoon has become more or less standardized at 20 milliliters. These are measures for food recipes, with a regional difference built into the tablespoon itself. The measure also goes by the name tablespoonful, and its abbreviations include tbsp and tblsp. A spoon name or its shortened form can therefore represent a defined recipe volume.
The smaller spoon brings consistency across those borders. In metric kitchens in Britain, Canada, Australia, and New Zealand, a teaspoonful is exactly 5 milliliters. The regional variation therefore occurs at the tablespoon level, rather than through a change in the size of the teaspoon. A metric tablespoon in an Australian recipe holds more of these equal teaspoonfuls than its counterpart in the other named countries. The smaller recipe measure also goes by teaspoon or teaspoonful, abbreviated tsp or t. These names sit beside tablespoon and tablespoonful in the kitchen vocabulary, linking the written recipe's short forms to the full names of its units.
Canada's traditional cooking measures belonged to the Imperial fluid-ounce system. Its tablespoon was half an Imperial fluid ounce, equivalent to 14.2 milliliters. Its traditional teaspoon was a sixth of an Imperial fluid ounce, or about 4.74 milliliters. Both spoon measures were thus smaller in milliliter terms than their Canadian metric counterparts. Within the traditional system, the tablespoon and teaspoon were linked through fractions of the same fluid ounce. That relationship gave the spoonfuls a common basis even though their volumes differed from the later metric sizes used for the same kitchen names.
In Britain, the traditional tablespoon had a range of sizes. Older references put it between half and five eighths of an Imperial fluid ounce, corresponding to about 14.2 through 17.8 milliliters. The British metric tablespoon falls within that older range. The change toward metric standardization therefore brought a named volume to a measure whose traditional size had varied. A British tablespoon from the older system might sit on either side of the metric size in milliliter terms. Its Imperial fraction identifies its capacity more precisely than the kitchen name alone, because that name covered differing traditional amounts.
Britain also had separate kitchen and medical teaspoonfuls. A traditional kitchen teaspoonful was an eighth of an Imperial fluid ounce, approximately 3.55 milliliters. The medical teaspoonful was usually 5 milliliters, giving it the same stated volume as the teaspoon in metric kitchens. Here the setting changed the quantity attached to the smaller spoon's name within the same country. The kitchen measure retained an Imperial fraction, while the medical spoon usually had the larger capacity. 'Usually' leaves room for variation in the medical measure; the metric kitchen teaspoon, by comparison, has an exact milliliter value.
The traditional British tablespoonful was often four teaspoonfuls, or a tenth of a teacupful. The teacupful was itself a liquid-volume measure used in British food recipes, equal to an Imperial gill. Its stated capacity was 5 Imperial fluid ounces, 8.670 cubic inches, or about 142.1 milliliters. This placed the spoonful inside a wider kitchen vocabulary that included cups as named quantities. Elsewhere, a tin became a kitchen unit: an English cigarette tin was formerly common for measuring ingredients in North Africa and the Middle East. That measure is still found in recipe books from the region. Its volume is approximately 8 Imperial fluid ounces, or 227 milliliters, roughly the same as a U.S. cup.
Across the Atlantic, the U.S. cooking tablespoon is half a fluid ounce, about 14.8 milliliters. It equals three teaspoons or a sixteenth of a cup. The U.S. teaspoon, in turn, is a third of a tablespoon or a forty-eighth of a cup, equivalent to a sixth of a fluid ounce. Its volume is about 0.30 cubic inches or approximately 4.9 milliliters. The U.S. tablespoon sits close in volume to the metric tablespoon used in Britain, Canada, and New Zealand, while retaining its own fluid-ounce and cup relationships.
At the bar, the same spoon names describe another set of volumes. U.S. bartenders use a tablespoon of three eighths of a fluid ounce, or a quarter of a jigger, equivalent to about 11.1 milliliters. Their teaspoon is an eighth of a fluid ounce or a twelfth of a jigger, about 3.7 milliliters. Both bartending spoon measures are smaller than the corresponding U.S. recipe measures. The bartender's tablespoon and teaspoon still connect through the same fluid ounce, with the larger holding three of the smaller measures.