What is the standard capacity of a Champagne bottle called a magnum?

A Champagne magnum has a standard capacity of 1.5 litres.

That volume equals two regular 750-millilitre wine bottles. Magnums are popular for celebrations and are also valued by many wine professionals because the larger format can provide a favourable ratio of wine to oxygen during ageing.

Champagne bottles come in a wide range of formats, from small individual bottles to very large ceremonial sizes. The names can vary by region or producer, so capacity is the clearest way to identify a format. A magnum is not the same as a jeroboam, which commonly holds 3 litres in Champagne terminology.

The bottle’s larger glass mass and shape require careful handling during riddling, disgorgement and transport. Although magnums are often associated with parties, they are also used for serious cellar ageing and formal service.