Guide

Whisky measures and bottle sizes around the world

From a 25ml British pub measure to a US fluid ounce: international whisky pours, bottle sizes, alcohol units and price per litre compared, at UK prices.

A whisky measure is not the same size everywhere. In a British pub, a single is generally 25ml or 35ml. An Irish pub measure is often described as 35.5ml. In the US, 1.5 fluid ounces is used as a health example of a standard drink, but it is not a promise of what any particular bar will pour. Even the fluid ounce changes size depending on which side of the Atlantic it comes from.

There are three different questions here: how much whisky is in the glass, how much is in the bottle, and how much pure alcohol it contains. This guide separates them so that a pour, a price and a drinking guideline are not mistaken for one another. For what may legally be called whisky in the first place, see whisky’s legal definitions by country.

A measure, a shot and a dram

In ordinary whisky conversation, dram means a serving, not a reliable quantity. A shot is not a dependable international unit either: the glass, bar and country can all make a difference. Ask for the volume if it matters, particularly when comparing prices or calculating alcohol intake.

The figures below are not all the same kind of rule. Some are rules for trade; others are health examples. A health organisation’s example of a standard drink measures alcohol, not the size a bartender is required to serve.

Sources: GOV.UK, Irish HSE, Irish price-display regulations, US NIAAA, Health Canada and Australia’s health department.

The British pub rule

For whisky sold by the glass in Great Britain, a premises normally chooses either 25ml or 35ml and sells multiples of that choice. A double is therefore 50ml in a 25ml premises or 70ml in a 35ml premises, not a universal size. The rule also applies to gin, rum and vodka. A notice should tell customers which measure is used. There are exceptions for certain mixed drinks; Cornwall Council’s trading standards guidance explains the cocktail exception and measuring equipment.

That is a trade rule, not a measure of how much a person should drink. Northern Ireland has separate weights-and-measures arrangements, so check local rules rather than assuming the Great Britain description covers every situation there.

Fluid ounces: US and imperial are different

The US National Institute of Standards and Technology gives these conversions:

That explains why the US and Canadian health examples both say 1.5 ounces but give approximately 44ml and 43ml respectively. A fluid ounce measures volume; an ounce without “fluid” can mean a unit of weight. They are not interchangeable.

Metric labels are easier to compare: 1 litre is 1,000ml, and 1 centilitre (cl) is 10ml. A 70cl bottle is 700ml; a 75cl bottle is 750ml. Neither number tells you how strong the whisky is.

Bottle sizes: 70cl, 75cl and beyond

The familiar full-size whisky bottle in Great Britain is 70cl, but 50cl, 35cl and one-litre bottles are also available. The GB rules for prepackaged spirit drinks specify permitted quantities from 100ml to 2,000ml inclusive: 100, 200, 350, 500, 700, 1,000, 1,500, 1,750 and 2,000ml. Outside that interval there are no specified quantities under this rule, which is why it does not prevent a 50ml miniature (see our guide to whisky miniatures and their cost per 70cl). The EU directive has the same listed spirit sizes in that interval; check the applicable rules for the market where a bottle is sold.

In the US, 750ml is a recognised spirits container size, as is 700ml. The US Alcohol and Tobacco Tax and Trade Bureau’s current list also includes sizes such as 50ml, 200ml, 375ml, 1 litre and 1.75 litres. It is not a rule that every US whisky must be 750ml. Check the label rather than assuming a bottle’s volume from its shape or origin.

These are theoretical whole pours from the stated volume, without spillage. The US-ounce column uses 44.36ml per pour and rounds the remainder.

Which bottle is better value?

Divide the price by the volume in litres. A 70cl bottle at £42 costs £60 per litre; a 75cl bottle at £45 also costs £60 per litre. The larger bottle costs more, but in this example the whisky costs the same per unit of volume. A 750ml bottle holds about 7.1% more than a 700ml bottle, not 50% more because the difference is 50ml.

This comparison does not account for delivery, availability, bottle condition or differences in the whisky itself. For offers from different shops, compare the delivered total for your order as well as the shelf price. Our guide to why whisky prices differ explains the wider comparison.

Volume is not the same as alcohol content

Two 25ml pours can contain different amounts of alcohol. The NHS calculation is:

UK alcohol units = volume in ml × ABV as a percentage ÷ 1,000.

One UK unit is 10ml, approximately 8g, of pure alcohol. Other countries use different standard-drink definitions: the US uses about 14g, Canada 13.45g and Australia 10g. Those are accounting measures, not recommended serving targets. The same whisky can therefore be described as a different number of units or standard drinks depending on the country and its ABV. Diluting it with water changes the strength in the glass, but does not remove the alcohol already poured. For higher-strength bottles, our guide to what cask strength whisky is explains how natural bottling strength affects pure alcohol content.

How we checked

We checked the linked government, public-health and measurement sources on 26 October 2026 and rechecked them on 27 October 2026. Legal requirements depend on jurisdiction and circumstances; the sections above are a practical summary, not legal advice. Calculations use labelled bottle volume and ABV, and results are rounded where stated.

About the author

John Fegan · Editor

Hailing from the land of haggis and deep-fried Mars bars, John was always going to find his way to whisky. He has run Uisge Beatha since 2015 and Whiskipedia.com since 2020.