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11 units — decimal (KB/MB/GB) and binary (KiB/MiB/GiB) side by side
Enter a value in any field — all 11 units recalculate
Type in any field
Decimal vs binary, side by side
Click Copy next to any value
| Unit | Abbreviation | System | Bytes |
|---|---|---|---|
| Byte | B | Base | 1 |
| Kilobyte | KB | Decimal (SI) — powers of 1000 | 10³ = 1,000 |
| Megabyte | MB | Decimal (SI) | 10⁶ = 1,000,000 |
| Gigabyte | GB | Decimal (SI) | 10⁹ = 1,000,000,000 |
| Terabyte | TB | Decimal (SI) | 10¹² = 1,000,000,000,000 |
| Petabyte | PB | Decimal (SI) | 10¹⁵ = 1,000,000,000,000,000 |
| Kibibyte | KiB | Binary (IEC) — powers of 1024 | 2¹⁰ = 1,024 |
| Mebibyte | MiB | Binary (IEC) | 2²⁰ = 1,048,576 |
| Gibibyte | GiB | Binary (IEC) | 2³⁰ = 1,073,741,824 |
| Tebibyte | TiB | Binary (IEC) | 2⁴⁰ = 1,099,511,627,776 |
| Pebibyte | PiB | Binary (IEC) | 2⁵⁰ = 1,125,899,906,842,624 |
This is the most common file size confusion — and it's not a scam. A 1 TB hard drive contains exactly 1,000,000,000,000 bytes (10¹²). Drive manufacturers use decimal prefixes as defined by the International System of Units (SI). Windows, however, calculates in binary (powers of 1024) but labels the result with decimal abbreviations (GB instead of GiB). So Windows takes 1,000,000,000,000 ÷ 1,073,741,824 (2³⁰) = 931.32 — and displays "931 GB." It's the same number of bytes, counted with a different-sized measuring cup. macOS has used decimal prefixes correctly since version 10.6 (Snow Leopard, 2009), so the same drive shows as "1 TB" on a Mac. Linux distributions vary: Ubuntu shows decimal by default, while many server distros use binary. This converter shows both systems simultaneously — toggle between decimal and binary to see exactly how the numbers diverge at each scale.
In December 1998, the International Electrotechnical Commission (IEC) introduced kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), and their larger siblings to resolve the 1024-vs-1000 ambiguity. The names combine the SI prefix with "bi" (binary): ki-lo-bi-nary = kibi, me-ga-bi-nary = mebi, gi-ga-bi-nary = gibi. The symbols add an "i": KiB, MiB, GiB. 25+ years later, adoption remains abysmal. Windows still uses "GB" to mean GiB. RAM is always measured in binary (a "16 GB" stick is 16 GiB = 17.18 GB). macOS is one of the few major operating systems to correctly use decimal prefixes. Hard drive and SSD boxes use decimal (the smaller number looks bigger). Network speeds (Mbps, Gbps) always use decimal. This converter makes the distinction visually obvious — decimal units on the left, binary on the right, so you can see at a glance how much they diverge.
| Scale | Decimal | Binary | Difference |
|---|---|---|---|
| Kilo | 1 KB = 1,000 B | 1 KiB = 1,024 B | 2.4% |
| Mega | 1 MB = 1,000,000 B | 1 MiB = 1,048,576 B | 4.86% |
| Giga | 1 GB = 1,000,000,000 B | 1 GiB = 1,073,741,824 B | 7.37% |
| Tera | 1 TB = 10¹² B | 1 TiB = 1,099,511,627,776 B | 9.95% |
| Peta | 1 PB = 10¹⁵ B | 1 PiB = 1,125,899,906,842,624 B | 12.59% |
The percentage gap compounds at each level — from a negligible 2.4% at the kilobyte level to over 12% at the petabyte level. This is why a "1 TB" SSD shows as ~931 GB in Windows: the 9.95% gap at tera-scale means you "lose" about 70 GB per advertised terabyte — purely from measurement differences, not actual missing space.
Enter your byte value in the Byte field. For decimal: divide by 1,000,000 for MB, or 1,000,000,000 for GB. For binary: divide by 1,048,576 for MiB, or 1,073,741,824 for GiB. This converter shows both systems at once — the decimal column on the left, binary on the right.
Windows uses binary math (1024³) but labels results as "GB" (which should mean 1000³). Your drive contains exactly 1,000,000,000,000 bytes. Windows divides by 1,073,741,824 and gets ~931 — then labels it "GB." No space is missing — it's the same bytes counted with different math. macOS uses correct decimal prefixes, so the same drive shows as "1 TB" on a Mac.
1 MB = 1,000,000 bytes (decimal). 1 MiB = 1,048,576 bytes (binary). The difference is ~4.86%. Hard drive manufacturers use MB, RAM uses MiB (but calls it MB), and your OS may use either. The IEC created MiB/KiB/GiB in 1998 to fix this ambiguity — see the explanation above for why almost nobody adopted them.
Decimal: 1 MB = 1,000 KB. Binary: 1 MiB = 1,024 KiB. The 2.4% difference at this level grows to ~10% at TB scale. Network speeds (Mbps) always use decimal. OS file managers usually use binary but label as decimal — except macOS which uses decimal correctly.
1 GB (decimal) = 1,000,000,000 bytes (10⁹). 1 GiB (binary) = 1,073,741,824 bytes (2³⁰). The binary version is about 7.37% larger. When you buy a "64 GB" phone, the manufacturer means 64,000,000,000 bytes. When the OS reports "64 GB" available, it may mean either — depending on the OS. The gap is about 4.4 GB at this scale.