Format Displays Size of Partitions or Logical Drives Larger Than 64 GB Incorrectly

When you use Format.com to format a partition or logical drive that is larger than 64 gigabytes (64 GB, or 68,719,476,736 bytes) in size, Format.com does not report the correct size of the drive being formatted at the beginning of the format process. However, as the formatting process progresses, the entire drive is formatted, and the correct formatted size is displayed when the operation is finished.

Format.com uses some 16-bit values internally to calculate the initial displayed size of the drive. Some of these variables overflow when the drive size is equal to or larger than 64 GB.

This is a display (or cosmetic) issue only; the drive is formatted to its full size.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

This problem does not occur if you format the drive from within Windows Explorer.

The initial, incorrect size that Format reports is drivesize - 64 GB. For example, if a partition or logical drive is 70.3 GB (75,484,122,112 bytes) in size, Format initially reports the drive as being 6.3 GB (6,764,579,840 bytes) in size. For additional information about other issues with drives larger than 64 GB, click the article number below to view the article in the Microsoft Knowledge Base: