Storage Unit Converter
Convert between digital storage units like KB, MB, GB, TB and their binary equivalents KiB, MiB, GiB, TiB.
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.
About Storage Unit Converter
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.
A Quick History of the Kilobyte Problem
The kilobyte has meant two different things for most of computing history. Early programmers used "kilo" to mean 1,024 because powers of 2 aligned with how memory hardware addresses data. A 1024-byte block was simply "1 KB" in manuals from the 1960s onward. At the same time, physicists and everyone else used "kilo" in its proper SI sense of 1,000. Both conventions persisted for decades because the gap at KB-scale (2.4%) was small enough to ignore.
The problem compounded at each higher prefix: a mebibyte is 4.9% larger than a megabyte, a gibibyte is 7.4% larger than a gigabyte, and a tebibyte is 10.0% larger than a terabyte. By the time drives crossed the terabyte boundary in the mid-2000s, the mismatch was impossible to ignore. This is why IEC 80000-13 (the standard that codified KiB, MiB, GiB) was published in 1998 and re-affirmed in 2008 - a clean separation between binary and decimal was overdue. NIST officially adopted the binary prefixes in 2005, and Linux utilities like ls -h and df -h use them by default today.
What Does 1 GB Actually Hold?
One gigabyte is roughly 1 billion bytes, but concrete examples make this easier to reason about. A plain text novel is about 1 MB, so 1 GB holds around 1,000 full-length books. A high-quality MP3 at 320 kbps is about 2.4 MB per minute of audio, meaning 1 GB stores roughly 7 hours of music. Smartphone photos from a modern 12-megapixel camera average 3-5 MB each, so 1 GB fits 200-300 photos. A 1080p Netflix stream uses about 3 GB per hour, while a 4K stream uses 7 GB per hour per Netflix's published figures.
| Content Type | Approximate Size | What 1 GB Holds |
|---|---|---|
| Plain text novel | 1 MB | ~1,000 books |
| MP3 audio (320 kbps) | 2.4 MB per minute | ~7 hours of music |
| Lossless FLAC audio | 30 MB per minute | ~33 minutes |
| 12 MP smartphone photo | 3-5 MB | ~200-300 photos |
| RAW photo (full-frame) | 30-50 MB | ~20-33 photos |
| 1080p Netflix stream | 3 GB per hour | ~20 minutes |
| 4K Netflix stream | 7 GB per hour | ~8-9 minutes |
| Blu-ray 4K movie rip | 50-70 GB | ~2% of one film |
At the other end, a single modern AAA game install ranges from 40 GB (Doom Eternal) to over 200 GB (Call of Duty Modern Warfare III). That is why 2 TB PlayStation 5 and Xbox Series X SSDs became standard after launch - a 1 TB drive holds only 5-6 triple-A titles at current install sizes.
How Big Is the Whole Internet?
Estimates of total global data vary, but IDC's Global DataSphere forecast (2024) puts created and captured data at roughly 181 zettabytes for 2025, rising to 394 ZB by 2028. One zettabyte is 10^21 bytes, or a billion terabytes. Most of this is ephemeral - sensor streams, video chat frames, machine-generated logs - and never persisted. Actively stored data is a much smaller subset, estimated at under 15% of the total.
For context, the Library of Congress print collection has been estimated at 10 terabytes of raw text (though a full digital mirror with images and manuscripts exceeds 3 petabytes per Library of Congress storage infrastructure reports). A single modern data centre holds millions of terabytes. Hyperscale facilities like those run by AWS, Google Cloud, and Microsoft Azure each cover 100,000 to 500,000 square feet and store exabytes of customer data.
| Scale | Bytes | Example |
|---|---|---|
| Kilobyte (KB) | 10^3 | A short email |
| Megabyte (MB) | 10^6 | A high-resolution photo |
| Gigabyte (GB) | 10^9 | A two-hour standard-def film |
| Terabyte (TB) | 10^12 | 200,000 songs |
| Petabyte (PB) | 10^15 | 2 billion digital photos |
| Exabyte (EB) | 10^18 | All words ever spoken by humans (rough) |
| Zettabyte (ZB) | 10^21 | About 6 months of global internet traffic |
| Yottabyte (YB) | 10^24 | Not yet in common use |
Why RAM Is Different
RAM is the one place where binary units are unambiguous. Memory chips are manufactured in powers of 2 (1 GiB, 2 GiB, 4 GiB, 8 GiB, 16 GiB, 32 GiB) because the address bus on a DRAM module physically addresses memory in binary. A "16 GB" stick of RAM holds exactly 17,179,869,184 bytes - that is 16 GiB, not 16 GB in the decimal sense. The label is technically wrong but universal, and because there is no "16 GiB in decimal" product to compare against, nobody notices.
The same applies to CPU cache sizes, GPU VRAM, and anything else soldered directly to silicon. This is worth knowing if you ever work with hex-to-decimal conversions while debugging memory addresses - the address space of a 32-bit system is exactly 2^32 bytes, or 4 GiB, not 4 GB decimal.
Common Conversion Mistakes
Three mistakes account for most storage-unit confusion:
- Confusing bits and bytes. Network speeds are in bits per second, file sizes are in bytes. A 100 Mbps connection downloads 12.5 MB per second, not 100 MB per second. The bold advertised number is always the larger one (bits) for marketing reasons.
- Mixing SI and IEC mid-calculation. Starting in GB but finishing in GiB (or vice versa) creates a 7% error. When totalling drive capacities, pick one system and stick with it throughout.
- Forgetting filesystem overhead. The formatted capacity of a drive is always less than the raw capacity. NTFS, APFS, and ext4 each reserve a few percent for metadata, journaling, and allocation tables. A freshly formatted 1 TB drive typically shows 930-935 GiB of usable space.
If a drive reports significantly less than the expected 93% after formatting, look for a hidden recovery partition (common on pre-built PCs and laptops) or a previously created volume that was not removed.
Sources
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.
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