Storage Unit Converter
Convert between digital storage units like KB, MB, GB, TB and their binary equivalents KiB, MiB, GiB, TiB.
About Storage Unit Converter
Digital storage is measured in two different systems - decimal (SI) using powers of 1,000 and binary (IEC) using powers of 1,024. This converter shows every unit in both systems simultaneously, so you can see exactly how a value in GB translates to GiB, MB, MiB, bytes, and everything in between.
Decimal (SI) vs Binary (IEC) Units
The confusion between these two systems is why a "500 GB" hard drive shows up as about 465 GB in your operating system. Drive manufacturers use decimal units (powers of 1,000), while many operating systems historically used binary math (powers of 1,024) but labelled the result as "GB" anyway.
| Decimal (SI) Unit | Symbol | Bytes | Binary (IEC) Unit | Symbol | Bytes |
|---|---|---|---|---|---|
| Kilobyte | KB | 1,000 | Kibibyte | KiB | 1,024 |
| Megabyte | MB | 1,000,000 | Mebibyte | MiB | 1,048,576 |
| Gigabyte | GB | 1,000,000,000 | Gibibyte | GiB | 1,073,741,824 |
| Terabyte | TB | 1,000,000,000,000 | Tebibyte | TiB | 1,099,511,627,776 |
| Petabyte | PB | 10^15 | Pebibyte | PiB | 2^50 |
The IEC introduced the binary prefixes (KiB, MiB, GiB) in 1998 to eliminate this confusion. The convention is slowly being adopted - macOS and iOS now display storage in decimal units, while Windows still uses binary calculations with decimal labels.
Why Drives Show Less Space Than Advertised
This is not a scam. Drive manufacturers correctly use decimal units (1 GB = 1,000,000,000 bytes), but when your OS uses binary math to display the size, the number appears smaller:
| Advertised Size (Decimal) | Displayed in Windows (Binary Math) | "Missing" Space | Percentage Difference |
|---|---|---|---|
| 128 GB | ~119 GiB | ~9 GB apparent | 7.0% |
| 256 GB | ~238 GiB | ~18 GB apparent | 7.0% |
| 500 GB | ~465 GiB | ~35 GB apparent | 7.0% |
| 1 TB | ~931 GiB | ~69 GB apparent | 6.9% |
| 2 TB | ~1,862 GiB | ~138 GB apparent | 6.9% |
| 4 TB | ~3,725 GiB | ~275 GB apparent | 6.9% |
| 8 TB | ~7,450 GiB | ~550 GB apparent | 6.9% |
The gap grows with larger drives in absolute terms, but stays around 7% proportionally. File system overhead (partition tables, journals, metadata) uses a small additional amount on top of this.
Which System Do Different Platforms Use?
| Platform / Context | System Used | Label | Notes |
|---|---|---|---|
| Windows | Binary (powers of 1,024) | KB, MB, GB (misleading) | Uses binary math but decimal labels |
| macOS (10.6+) | Decimal (powers of 1,000) | KB, MB, GB | Switched to decimal in 2009 |
| Linux (varies) | Both, depending on tool | KiB/MiB/GiB or KB/MB/GB | Many tools now correctly use IEC labels |
| iOS / Android | Decimal | GB | Matches what the box says |
| Drive manufacturers | Decimal | GB, TB | Industry standard, legally correct |
| RAM | Binary | GB (but actually GiB) | RAM is always in powers of 2 (4 GiB, 8 GiB, 16 GiB) |
| Network speeds | Decimal (bits) | Mbps, Gbps | 1 Gbps = 1,000,000,000 bits per second |
Common Storage Sizes Reference
| Media | Capacity (Decimal) | Capacity (Binary) |
|---|---|---|
| CD-ROM | 700 MB | ~667 MiB |
| DVD (single layer) | 4.7 GB | ~4.38 GiB |
| DVD (dual layer) | 8.5 GB | ~7.92 GiB |
| Blu-ray (single layer) | 25 GB | ~23.28 GiB |
| Blu-ray (dual layer) | 50 GB | ~46.57 GiB |
| USB flash drive (common) | 32 GB / 64 GB / 128 GB | ~29.8 / 59.6 / 119.2 GiB |
| microSD (common) | 128 GB / 256 GB / 512 GB | ~119.2 / 238.4 / 476.8 GiB |
Bits vs Bytes
Storage is measured in bytes. Network speeds are measured in bits. There are 8 bits in 1 byte. This is a separate distinction from the decimal/binary split:
| Measurement | Unit | Context |
|---|---|---|
| File size | Bytes (B, KB, MB, GB, TB) | How much space a file takes on disk |
| Network speed | Bits per second (bps, Kbps, Mbps, Gbps) | How fast data moves over a connection |
| Transfer rate | Bytes per second (B/s, KB/s, MB/s) | How fast data is written or read |
A 100 Mbps internet connection transfers 100 megabits per second, which is 12.5 megabytes per second (100 / 8). This catches people off guard when downloading files.
For network-related conversions, try the bandwidth calculator. If you need to estimate file transfer times at different connection speeds, the file transfer calculator covers USB, WiFi, Ethernet, and more. This tool runs entirely in your browser with no data sent to any server.
Frequently Asked Questions
What is the difference between GB and GiB?
GB (gigabyte) uses the decimal system where 1 GB equals 1,000,000,000 bytes. GiB (gibibyte) uses the binary system where 1 GiB equals 1,073,741,824 bytes. Storage manufacturers use GB while operating systems often report in GiB, which is why a 1 TB drive shows about 931 GiB.
Why does my 1 TB hard drive only show 931 GB?
Your drive really does hold 1 trillion bytes. The discrepancy comes from your operating system reporting in binary units (GiB) while labelling them GB. 1 trillion bytes divided by 1,073,741,824 gives roughly 931 GiB.
Which system should I use for networking calculations?
Networking uses the decimal (SI) system. Speeds like 100 Mbps refer to 100 million bits per second (base 10). RAM and file systems typically use binary units.
How many MB are in a GB?
In the decimal (SI) system, 1 GB equals 1,000 MB. In the binary (IEC) system, 1 GiB equals 1,024 MiB.
What does IEC stand for?
IEC stands for International Electrotechnical Commission. They introduced the binary prefixes (KiB, MiB, GiB, TiB) in 1998 to remove the ambiguity between decimal and binary interpretations of KB, MB, GB.
Related Tools
Link to this tool
Copy this HTML to link to this tool from your website or blog.
<a href="https://toolboxkit.io/tools/storage-converter/" title="Storage Unit Converter - Free Online Tool">Try Storage Unit Converter on ToolboxKit.io</a>