Mac OS Extended Format (HFS+): Default Allocation Block Size

This article provides a table that lists the default allocation block size for Mac OS Extended format volumes of various sizes.
This article has been archived and is no longer updated by Apple.
Volume Size
Default Allocation Block Size
<=256 MB
512 bytes
256 MB <= 512 MB
1024 bytes (1K)
512 MB <= 1 GB
2048 bytes (2K)
> 1 GB
4096 bytes (4K)
Last Modified: Feb 18, 2012

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