The jigger, the spoons and the jug
A recipe prints 30 ml and leaves you to own whatever holds 30 ml. Every measure on a recipe page has a tip beside it naming the tool it takes and how to pour it; these are those tools, side by side, in the sizes they are made in on both sides of the Atlantic.
Jigger
Two cones meeting at a waist, one pour in each. A spirit is measured into the small side or the large one, and the tip on a recipe names which.
| Part of it | Metric | American |
|---|---|---|
| Small side | 25 ml | 3/4 oz |
| Large side | 50 ml | 1 1/2 oz |
Spoons
A level teaspoon and a tablespoon, which is what everything under the jigger's small side is measured with - and what finishes a pour that is not a whole number of jiggers.
| Part of it | Metric | American |
|---|---|---|
| A teaspoon | 5 ml | 1/6 oz |
| A tablespoon | 15 ml | 1/2 oz |
Measuring jug
For the amounts that would take four pours of a jigger: a pitcher, a punch, the soda for a round. A jug holds whatever its marks say, so the size to buy is the one that covers the batch.
| Part of it | Metric | American |
|---|---|---|
| A quarter litre | 250 ml | 1 1/8 cups |
| Half a litre | 500 ml | 2 1/8 cups |
| A litre | 1 l | 4 1/4 cups |
The two columns are two tools rather than two names for one, so they are not the same pour: 50 ml (1 3/4 oz) is not the American 1 1/2 oz (44 ml). The two spoons are much closer - a metric teaspoon is 5 ml and an American one a sixth of an ounce, a hair under it - which is why a tip says "a teaspoon" on both sides of the Atlantic.
Two of the things a recipe measures with have no size here, because they are not measures: a dash is a quick shake of the bottle, about a millilitre and no two authors agree on it, and a splash is poured by eye - about two teaspoons, and freely. A pinch sits between the two: what comes up between finger and thumb, about a quarter of a teaspoon.
What this page cannot answer is the question a reader arrives with in their hand - what this measure is, the one they are looking at. That is one measure at a time, so it is a page of its own rather than a column here: convert a measure, with the size you wrote in the address so the answer can be linked to.
Which set of units a recipe page prints is a setting on the reader rather than on the drink: millilitres by default, American measures if you ask for them in your profile. A page's tip is worked out from the number as that page prints it, so the advice and the measure beside it always describe the same pour.