Storage & File Size Calculator
Convert file and storage sizes between decimal (KB, MB, GB) and binary (KiB, MiB, GiB) units and understand why they differ.
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How many files fit?
Approximately 40 files fit.
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What is the Storage & File Size Calculator?
This converter translates a size between decimal SI units (powers of 1000) and binary IEC units (powers of 1024), the source of the classic “missing gigabytes” confusion.
How to use it
- 1Enter a value and pick its unit.
- 2Read the equivalent in every other unit.
How it works
Everything is normalized to bytes. Decimal units multiply by 1000ⁿ; binary units multiply by 1024ⁿ. A “1 TB” drive holds 1,000,000,000,000 bytes ≈ 931 GiB.
Limitations & notes
- Rounding is applied for display; the byte value is exact.
Frequently asked questions
Why does my 1 TB drive show only 931 GB?
The drive holds 1,000,000,000,000 bytes, as sold. Windows divides by 1024 three times and labels the result GB, so it shows about 931.32, which is really 931 GiB. Nothing is missing. macOS has used decimal units since 2009, so the same drive shows close to 1 TB there, minus any formatting overhead.
Is a kilobyte 1000 or 1024 bytes?
By the international standard, a kilobyte (KB) is 1000 bytes and a kibibyte (KiB) is 1024 bytes. In practice RAM is sold in binary sizes, drives and network speeds in decimal, and Windows reports binary values with decimal labels. The gap grows with each step: about 2.4% at KB, 7.4% at GB and 10% at TB.
How many photos or videos fit on my drive?
Use the How many files fit section: enter the total capacity at the top and the size of one file below. For example, 1 GiB holds 40 files of 25 MiB, and a 256 GB card holds about 10,240 photos of 25 MB. The count is rounded down and assumes every file is the same size.
Why does a drive hold slightly fewer files than calculated?
Filesystems store files in clusters or blocks, commonly 4 KiB, so a 1 KiB file still occupies 4 KiB on disk. Drives also reserve space for the filesystem tables, journal and, on many systems, snapshots or recovery partitions. Large files lose little to clusters, but thousands of tiny files can use noticeably more space than their combined size.
Which units does this converter support?
It converts bytes, decimal KB, MB, GB and TB, and binary KiB, MiB, GiB and TiB, all from one entered value. Petabytes are not offered, so enter large sizes in TB or TiB, for example 2000 TB for 2 PB. The underlying byte value is exact; only the displayed result is rounded to four decimal places.
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