Shot Size Converter (oz ⇄ mL)

Understanding the shot size converter — concept and principle

This converter changes bar and cocktail measures between millilitres, US fluid ounces, UK fluid ounces, the US shot and jigger (1.5 US fl oz) and the UK single (25 mL) and double (50 mL) measures. Use it to follow an American cocktail recipe with metric jiggers, compare a UK pub measure with a US shot, or scale a recipe for a party.

How it is calculated

The value is converted to millilitres and then divided by the size of the target unit: result = value × (mL per "from" unit) ÷ (mL per "to" unit). The factors are:

• 1 US fl oz = 29.5735295625 mL (1/128 of a US gallon of 231 cubic inches, exact).
• 1 UK fl oz = 28.4130625 mL (1/160 of an imperial gallon of 4.54609 L, exact).
• US shot or jigger = 1.5 US fl oz = 44.36029434 mL.
• UK single = 25 mL, UK double = 50 mL.

The principle

The US and UK fluid ounce have the same name but come from different gallons, and the UK ounce is about 4 % smaller. A "shot" is not one international unit; it is a serving convention. In the US the usual pour is 1.5 fl oz, while UK bars use metric measures, commonly 25 mL or 35 mL for spirits. Converting through millilitres removes the ambiguity, because every bar measure can be expressed exactly in the SI-based litre.

Worked example

Default inputs: 1 US shot converted to millilitres.

1. A US shot is 1.5 US fl oz.
2. Convert: 1.5 × 29.5735295625 mL = 44.36029434 mL.
3. Result: 1 US shot = 44.36029434 mL, about 44.4 mL.
4. The same amount is 1.5 US fl oz, 1.561 UK fl oz, 1.774 UK singles (25 mL) or 0.887 of a UK double (50 mL).

How to read the result

A US shot of about 44 mL is noticeably larger than a UK single of 25 mL, so a "single" ordered in the UK contains roughly 56 % of the spirit in a US shot. For cocktail recipes, 1 oz is often rounded to 30 mL by bartenders; that is close enough for mixing (about 1.4 % off), but use the exact factor for nutrition or cost calculations. Small cocktail jiggers are often marked 1 oz / 2 oz or 25 mL / 50 mL, so check which side you are using.

Common mistakes

• Mixing up US and UK fluid ounces in older British recipes.
• Assuming every "shot glass" holds 1.5 oz; souvenir and Korean soju glasses vary widely.
• Treating "jigger" as one fixed size; double-sided jiggers have two different cups.
• Forgetting that alcohol content depends on strength (ABV), not only on volume.

FAQ

Frequently asked questions

How many mL is a shot?

A US shot is 1.5 US fl oz = 44.36 mL; a UK single measure is usually 25 mL.

How many mL is 1 oz?

1 US fl oz = 29.57 mL; 1 UK fl oz = 28.41 mL.

Is a jigger the same as a shot?

In US usage a standard jigger is 1.5 fl oz, the same as a shot, but many jiggers have a second, different cup.

Sources: NIST Special Publication 811 (2008), Appendix B, conversion factors · NIST Handbook 44, Appendix C, General Tables of Units of Measurement