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Enter your target partition size in GB to calculate the MB value needed for an exact whole-number display in Windows—no more 99.9 GB partitions.
Enter the partition size you want the system to display as a whole number, in GB.
NTFS is estimated using cylinder alignment; FAT32 uses a commonly used whole-number partition formula.
Enter a target size to view the recommended MB values for NTFS and FAT32.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
Enter a whole-number target in GB and the calculator returns suggested entry sizes in MB for NTFS and FAT32. It accepts integer targets from 1 through 32,768 GB. The result is a planning estimate: it does not inspect your drive, select a file system, create a partition, or promise that Windows will show an exact whole-number capacity after formatting.
The tool uses 1,024 MB per GB for its baseline, then applies a separate adjustment to each file-system result. For NTFS, it estimates cylinder alignment using 7.84423828125 MB as the cylinder size, rounds the estimated cylinder count down, and adds one cylinder-sized alignment step plus one MB. For FAT32, it uses the calculator’s simple adjustment of four MB per target GB after the first GB. These are the tool’s calculation rules, not a Microsoft standard or a guarantee for every drive and formatting setup.
Baseline MB = target GB × 1,024
NTFS estimate = floor((floor(baseline MB ÷ 7.84423828125) + 1) × 7.84423828125) + 1
FAT32 estimate = baseline MB + (target GB − 1) × 4
For a 100 GB target, the baseline is 102,400 MB. The FAT32 estimate is 102,796 MB; the NTFS result follows the alignment calculation and may be different. Microsoft’s NTFS documentation describes file-system metadata such as the Master File Table, whose size can change as files are added; it does not establish the calculator’s fixed formula as an official Windows rule.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Enter a positive whole-number GB capacity, or choose one of the common-size buttons.
Compare the baseline conversion with the NTFS and FAT32 suggested MB entries. The table also gives examples for common target sizes.
If you decide to partition a disk, confirm the available unallocated space and the selected file system in your operating system’s partitioning workflow. Copy the relevant MB value only after checking that it fits.
You can copy either suggested value from its result card. The calculator does not reserve space for recovery partitions or other partitions you may need.
Use cases
See how the tool fits into real work and everyday tasks.
Before dividing a blank drive, compare proposed target sizes and their two suggested MB entries. Add the planned partitions together and leave room for any system or recovery volumes required by your setup.
If a setup screen asks for a partition size in MB, use the estimate as a starting point, then verify the selected disk, file system, and remaining capacity before applying changes.
Q&A
Find concise answers to common questions and confusing cases.
The calculator applies different adjustment rules to each result. They are estimates intended to help plan an entry, not universal file-system guarantees.
No. The result does not account for every disk layout, formatting choice, or system partition. Check the capacity shown after formatting.
No. The input accepts whole numbers from 1 to 32,768 GB.
Notes
Review scope, result limitations, and important precautions before use.
Partition creation, deletion, and formatting can make existing data inaccessible or erase it. Back up files you need and verify the correct disk and partition before applying changes. The calculator does not detect disk capacity, alignment requirements, operating-system constraints, or the layout already present on your drive.
Its GB-to-MB baseline is binary (1 GB is treated as 1,024 MB). Drive labels and other operating systems may use different capacity conventions. Treat each output as an estimate for manual planning, not as a measured usable-capacity result.
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