Cork Sizes

Choosing the Wine Cork Size

Selecting the correct cork size is crucial to ensuring a proper seal and supporting the wine’s maturation process. Cork dimensions are typically measured in millimeters, with the length listed first and the diameter second.

Cork Diameter: Ensuring a Proper Seal

The cork’s diameter plays a key role in creating an airtight seal. A natural cork should be at least 6 mm wider than the narrowest part of the bottle’s neck. However, excessive compression—over 33% of the cork’s original diameter—can damage its cellular structure, affecting its sealing ability.

21 mm diameter (size #7) – Can be inserted by hand but is not recommended for long-term storage, as the seal is weaker and prone to leakage. Bottles sealed with #7 corks should be stored upright.
22 mm diameter (size #8) – A slightly smaller option, requiring a wine bottle corker for insertion.
24 mm diameter (size #9) – The most common size, used by commercial wineries for standard 750 ml wine bottles.

For corkers, 22 mm corks fit most devices, but 24 mm corks may require specialized corkers to avoid fraying.

Cork Length: Impact on Maturation

Once the diameter is chosen, the length of the cork further affects the quality of the seal and the aging potential of the wine. Longer corks are typically used for wines intended for extended maturation.

44 mm length – The industry standard for most 750 ml bottles.
38 mm length – Often used for 375 ml half-bottles or wines intended for shorter aging.
54 mm length – Provides a superior seal for premium wines meant for long-term cellaring.

To maintain an optimal seal, there should be about 20 mm of space between the bottom of the cork and the wine level. Standard 750 ml bottles can generally accommodate corks between 38 mm and 54 mm, depending on the bottle design and storage conditions.

A more standardized classification, such as that used by the United States Cork Quality Council (CQC), divides corks into three categories: