Keep in mind it goes further than that. US customary volume units don't match up with British ones.

One British gallon is about 4.5 liters, where a US gallon is about 3.8. Quarts, pints, and cups follow, but fluid ounces are another thing. A US gallon is divided into 128 fl. oz., while a British gallon is 160. This results in a US fluid ounce of about 29.6 ml, vs. 28.4 ml for the British one, and also affects teaspoons and tablespoons.

▲ kruador a day ago | parent [-]

Strictly, UK teaspoons are 5 ml and tablespoons 15 ml. The metric tablespoons already used in Europe were probably close enough to half an Imperial fluid ounce for it not to matter for most purposes.

My kids' baby bottles were labelled with measurements in metric (30 ml increments) and in both US and Imperial fluid ounces. The cans of formula were supplied with scoops for measuring the powder, which were also somewhere close to 2 tablespoons/one fluid ounce (use one scoop per 30 ml of water). There are dire warnings about not varying the concentration from the recommended amount, but I assume that it's not really that precise within 1-2% - more about not varying by 10-20%. My kids seem to have survived, anyway.

	▲	inferiorhuman a day ago \| parent [-]
		`Strictly, UK teaspoons are 5 ml and tablespoons 15 ml.` Well there's a rabbit hole I wasn't expecting to go down. I knew that Australian tablespoons (20 mL) were significantly different from US tablespoons. I didn't know that UK tablespoons were a whole different beast (14.2 mL), nor did I realize US tablespoons aren't quite 15 mL, and in fact my tablespoon measures are marked 15 mL. 15 mL is handily 1/16 of a US cup so it's easy enough to translate to 1/4 cup (4 tsbsp) and 1/3 cup (5 tbsp). https://en.wikipedia.org/wiki/Tablespoon