Data Storage Unit Converter
Convert between bits, bytes, and the full SI/IEC family — KB, MB, GB, TB, PB plus their binary cousins KiB, MiB, GiB, TiB, PiB — using IEC 80000-13 definitions. Type a value and the conversion is instant.
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Why are there two families of data storage units?
Computers count in binary, but humans count in decimal — and that single mismatch is why you have two kilobytes, two megabytes, and two gigabytes. The decimal family (KB = 1,000 B, MB = 1,000,000 B, GB = 1,000,000,000 B) follows the same SI prefix rule as kilometres and kilograms: each step is a factor of 10³. The binary family (KiB = 1,024 B, MiB = 1,048,576 B, GiB = 1,073,741,824 B) follows powers of 2: each step is 2¹⁰. The two diverge by 2.4% at kilo, 4.9% at mega, 7.4% at giga, 10.0% at tera, and 12.6% at peta — large enough to be visible on every storage label and operating system you own.
Until 1998 the industry used "KB", "MB", and "GB" for both senses, decided by context. The IEC then introduced the unambiguous binary prefixes — kibi, mebi, gibi, tebi, pebi — and IEEE 1541-2002 ratified them. Today most operating systems and the file-system specs follow IEC 80000-13: KB/MB/GB mean decimal, KiB/MiB/GiB mean binary. Hard-drive manufacturers and networking gear use decimal; RAM, file sizes in Windows and the Linux kernel report binary; macOS and iOS switched to decimal in 2009. Knowing which family you're looking at explains most of the "missing storage" mysteries on consumer devices.
The data storage units, explained
Bit and byte — the base units
A bit is the smallest unit of digital information: a single binary 0 or 1. A byte is 8 bits, the smallest addressable unit on virtually every modern computer. The factor 1 B = 8 bit goes back to the IBM System/360 in the 1960s, when 8-bit characters became the de-facto standard. The lower-case "b" is a bit; the upper-case "B" is a byte — a distinction that matters most for network speeds, where a "100 Mbps" link transfers about 12.5 MB/s once you divide by 8.
Decimal prefixes (KB, MB, GB, TB, PB) — SI standard
Each step is a factor of 1,000. So 1 KB = 1,000 B, 1 MB = 1,000 KB = 10⁶ B, 1 GB = 10⁹ B, 1 TB = 10¹² B, 1 PB = 10¹⁵ B. These match the SI kilo-, mega-, giga-, tera-, peta- prefixes you already know from grams and meters. Hard drives, SSDs, USB sticks, and network bandwidth are all advertised in decimal units.
Binary prefixes (KiB, MiB, GiB, TiB, PiB) — IEC 80000-13
Each step is a factor of 1,024 = 2¹⁰. So 1 KiB = 1,024 B, 1 MiB = 1,048,576 B, 1 GiB = 1,073,741,824 B, 1 TiB ≈ 1.0995×10¹² B, 1 PiB ≈ 1.1259×10¹⁵ B. These prefixes — kibi-, mebi-, gibi-, tebi-, pebi- — are pronounced "kibby, mebby, gibby, tebby, pebby". They appear in RAM specifications, in the way Windows and Linux report file sizes, and in academic computer science.
Bits vs bytes — the network catch
Networking has historically used bits per second (bps, Mbps, Gbps) because data on a wire is serial and naturally bit-clocked. Storage has always used bytes (B/s, MB/s). A 1 Gbps fibre line transfers about 125 MB/s — divide bps by 8 to get B/s. Always check whether your speed is a lower-case "b" (bits) or upper-case "B" (bytes); the factor of 8 is enormous for billing, planning, and sizing back-ups.
Real-world numbers across the data storage units
- A single character: ASCII text: 1 byte per character. UTF-8: 1–4 bytes per character; English averages ~1, accented Latin ~2, Chinese/Japanese/Korean ~3.
- Photos and music: A 12-megapixel JPEG: 3–6 MB. A 4K HDR raw photo: 30–80 MB. A 4-minute 320 kbps MP3: about 9.6 MB. A lossless FLAC of the same song: ~30 MB.
- Video files: 1 minute of 1080p H.264 at 8 Mbps: 60 MB. 1 hour of 4K H.265 at 50 Mbps: about 22 GB. A 90-minute Blu-ray rip in 1080p: 8–25 GB depending on codec.
- RAM and CPU caches: RAM is sized in binary units. "16 GB" of laptop RAM is really 16 GiB = 17,179,869,184 bytes. CPU L1 caches are tens of KiB; L2 around 1 MiB; L3 from 4 MiB to 64 MiB depending on chip.
- Hard drives and SSDs: Drive makers always use decimal. A "1 TB" SSD is exactly 1,000,000,000,000 bytes = 931.32 GiB on disk. A "4 TB" drive shows 3,725 GiB. The discrepancy is the binary/decimal mismatch, not a defect.
- Network bandwidth: Home broadband marketed as "100 Mbps" delivers ~12.5 MB/s of file transfer once you divide by 8 and shave protocol overhead. "1 Gbps fibre" peaks around 110–115 MB/s in practice. ISPs almost always advertise in megabits per second.
- Cloud and data-centre scale: A modern hyperscaler stores exabytes (EB = 10¹⁸ B). A typical enterprise database runs in single-digit terabytes; a content-delivery network's edge cache, hundreds of terabytes per pop. Backups are sized in TB or PB.
How much is 1 unit of each in bytes?
| Unit | Value in bytes (B) |
|---|---|
| 1 bit (Bit) | 0.125 Pa |
| 1 B (Byte) | 1 Pa |
| 1 KB (Kilobyte (decimal)) | 1000 Pa |
| 1 MB (Megabyte (decimal)) | 1000000 Pa |
| 1 GB (Gigabyte (decimal)) | 1000000000 Pa |
| 1 TB (Terabyte (decimal)) | 1000000000000 Pa |
| 1 PB (Petabyte (decimal)) | 1000000000000000 Pa |
| 1 KiB (Kibibyte (binary)) | 1024 Pa |
| 1 MiB (Mebibyte (binary)) | 1048576 Pa |
| 1 GiB (Gibibyte (binary)) | 1073741824 Pa |
| 1 TiB (Tebibyte (binary)) | 1099511627776 Pa |
| 1 PiB (Pebibyte (binary)) | 1125899906842624 Pa |
Frequently asked questions about data storage units
What's the difference between MB and MiB, or GB and GiB?
Decimal vs binary. 1 MB = 1,000,000 bytes (10⁶). 1 MiB = 1,048,576 bytes (2²⁰). 1 GB = 10⁹ bytes; 1 GiB = 2³⁰ ≈ 1.074 × 10⁹ bytes. The IEC introduced KiB/MiB/GiB in 1998 to remove the long-standing ambiguity around "KB". Use decimal for storage marketing and bandwidth, binary for memory and OS-reported sizes.
Why does my 1 TB drive show 931 GB in Windows?
Drive manufacturers use decimal: "1 TB" means exactly 10¹² = 1,000,000,000,000 bytes. Windows reports sizes in binary (gibibytes) but labels them "GB" — so it shows 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GB. The drive is full size; it's a labelling convention. macOS and iOS switched to decimal in 2009 (Snow Leopard / iOS 4) and now show drives at their advertised capacity.
Are network speeds in megabits or megabytes?
Almost always megabits per second (Mbps), with a lower-case "b". A "100 Mbps" connection transfers up to 100,000,000 bits per second = 12.5 MB/s of raw payload. Real-world download speeds are 5–10% lower because of TCP/IP overhead. To convert: divide bits per second by 8 to get bytes per second. Storage I/O speeds (SSD, USB) are usually quoted in MB/s — bytes.
How many bits in a byte?
8 — the modern standard. Earlier mainframes used 6, 7, or 9-bit bytes, but every commodity computer since the 1970s has used 8-bit bytes. The formal name is octet (8 bits), used in RFCs and telecommunications standards to remove any ambiguity.
What's a kibibyte and how do you pronounce it?
A kibibyte (KiB) is exactly 1,024 bytes — the binary version of "kilobyte". Pronounce it "kibby-byte". The full set: KiB (kibby), MiB (mebby), GiB (gibby), TiB (tebby), PiB (pebby), EiB (exby), ZiB (zebby), YiB (yobby). Awkward sounding but unambiguous.
Is 1 GB really 1024 MB or 1000 MB?
Officially 1 GB = 1,000 MB (decimal, IEC 80000-13). The 1,024 MB figure refers to a gibibyte (1 GiB). Many older Microsoft products and some game documentation conflated the two — saying "1 GB = 1,024 MB" — but the formal SI/IEC standard is unambiguous: GB is decimal, GiB is binary.
How much storage does a modern smartphone need?
iPhone and high-end Android base storage is now 128 GB to 1 TB. The OS itself takes 8–15 GB. Photos average 3 MB each (1,000 photos ≈ 3 GB). 4K video shot at 60 fps consumes around 400 MB per minute. Music streaming caches 50–500 MB; offline maps for one country, 1–4 GB.
What does Mb/s mean vs MB/s?
Capital matters. Mb/s (or Mbit/s, Mbps) = megabits per second — used for bandwidth. MB/s (or MByte/s) = megabytes per second — used for file I/O. 1 MB/s = 8 Mb/s. A 100 Mbps internet plan transfers 12.5 MB/s; an SSD rated 500 MB/s transfers 4,000 Mbps.
What's bigger — petabyte, exabyte, or zettabyte?
Each step up is a factor of 1,000 (decimal SI): KB → MB → GB → TB → PB → EB → ZB → YB. PB = 10¹⁵, EB = 10¹⁸, ZB = 10²¹, YB = 10²⁴. Global internet traffic is now in the hundreds of zettabytes per year. The IEC binary equivalents continue: PiB, EiB, ZiB, YiB.
Can I link to a specific data conversion?
Yes. The URL updates as you change units and values. Example: ?from=GB&to=GiB&x=1000 shows how a 1 TB drive shrinks to 931 GiB. Copy the address bar to share or bookmark.
References
Dedicated converter pages
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