Overview
The gap between the capacity printed on a drive's box and the capacity Windows actually shows is one of the oldest sources of confusion in all of computing, purely because manufacturers calculate gigabytes using powers of ten (1,000,000,000 bytes per GB) while Windows displays capacity using powers of two (1,073,741,824 bytes per "GB", more precisely a gibibyte). Drive Capacity Checker sidesteps the confusion entirely by reporting both the exact raw byte count and a clean decimal-gigabyte figure for every attached drive, so there is no ambiguity about what a given number actually means.
Key Features
- Reports each drive's exact raw capacity down to the byte
- Converts raw bytes into a clean, decimal gigabyte figure for readability
- Shows the drive's model alongside its capacity for identification
- Covers every attached physical disk, internal and external
Why You Might Need This Tool
"Why does my new 1TB drive only show 931GB in Windows" is one of the most frequently asked storage questions online, and the honest answer is that nothing is wrong — it is purely a units mismatch between decimal marketing gigabytes and binary Windows gigabytes, and every drive from every manufacturer exhibits the exact same gap. Having the precise raw byte count on hand settles the question definitively, and is also genuinely useful when comparing two drives that are supposedly the same capacity but come from different manufacturers or product lines, where small real-world differences do occasionally exist.
How It Works
The tool queries Win32_DiskDrive through WMI for the Size
field, which Windows reports as an exact byte count derived from the drive's own
reported sector count and sector size during enumeration. The tool then computes a
decimal-gigabyte figure by dividing that raw byte count by 1,000,000,000, matching
the same calculation method drive manufacturers use on product packaging, while
still displaying the untouched raw byte figure alongside it for anyone who wants the
exact, unrounded number.
How to Use It
Open the program and every attached drive's raw byte count and decimal-gigabyte figure appear immediately, with no configuration needed.
System Requirements & Notes
Runs on 64-bit Windows 10/11 with no administrator rights required.
Frequently Asked Questions
Is my drive defective if it shows less than the advertised capacity?
Almost certainly not — a few percent difference between advertised and reported
capacity is the expected decimal-vs-binary gigabyte gap, not a sign of a faulty or
counterfeit drive.
How can I tell if a drive genuinely has fake, inflated capacity?
A drive reporting a wildly larger capacity than what actually works reliably is a
different problem entirely — see
Flash Drive / Card Tester, which is built
specifically to catch that.
Does formatting reduce the reported raw capacity?
Formatting reserves a small amount of space for filesystem metadata, which is why
the usable space shown in File Explorer is always slightly less than this tool's raw
drive-level figure.