Windows Disk Partition Calculator
Calculate exact MB values for Windows partitions to display as perfect integer GB. Solve partition size display issues with NTFS and FAT32 file systems.
The size you want to see in Windows Explorer (e.g., 10.00 GB)
Modern Windows setup creates 3 hidden partitions for the first primary partition
Windows Disk Partition Calculator Guide
Complete guide to calculating accurate partition sizes for Windows NTFS and FAT32 file systems
Q: Why does my 10GB partition show as 9.77GB in Windows?
This happens because partitioning tools use binary calculation (1024-based) while Windows Explorer uses a special display algorithm. When you enter 10240MB, Windows shows ~9.77GB instead of 10.00GB.
The solution: Use our calculator to get the exact MB value needed for Windows to display your desired GB amount as a clean integer.
Q: What's the difference between NTFS and FAT32 calculations?
NTFS: Modern file system with advanced features. Uses multiplier of 1024.5
FAT32: Legacy but compatible file system. Uses multiplier of 1027.6
The different overhead means FAT32 requires slightly more MB to display the same GB in Windows.
Q: What is "first primary partition" and why does it matter?
When creating the first partition on an empty disk, modern Windows setup automatically creates 3 hidden system partitions:
- System Reserved Partition (~100MB) - Boot manager storage
- EFI System Partition (~300MB) - UEFI boot information
- Recovery Partition (~150MB) - Windows recovery environment
Total: 566MB additional space is automatically reserved by Windows.
Q: What are the exact calculation formulas?
NTFS partition: MB = Desired_GB × 1024.5
FAT32 partition: MB = Desired_GB × 1027.6
First primary: Add 566MB to above result