💾 Data Storage Unit Converter
Convert a value between bits, bytes, KB, MB, GB, TB, and PB, and see it expanded in both the decimal (SI) and binary (IEC) systems — the clearest way to understand real storage sizes.
💾 Exact size
📐 Full breakdown — both systems
| Unit | Decimal (SI) | Binary (IEC) |
|---|---|---|
| bits | 8,000,000,000,000 | 8,000,000,000,000 |
| bytes | 1,000,000,000,000 | 1,000,000,000,000 |
| KB | 1,000,000,000 | 976,563,000 |
| MB | 1,000,000 | 953,674 |
| GB | 1,000 | 931.323 |
| TB | 1 | 0.909495 |
| PB | 0.001 | 0.000888 |
Decimal columns use the SI names (KB, MB, GB…); binary columns are the IEC values a drive would report as KiB, MiB, GiB… This is why a “1 TB” (decimal) drive shows as about 931 GB in Windows.
Decimal vs binary, made clear
The gap between a drive's advertised size and what your computer reports is not a defect or lost space — it is two counting systems sharing the same names. Manufacturers use decimal units where a gigabyte is a billion bytes; operating systems mostly use binary units where a gigabyte is 1,073,741,824 bytes. Convert once and you can read either number with confidence.
Understanding this also helps when a backup “does not fit,” when a download size looks off, or when you are sizing an SSD upgrade. Pair it with the Download Time Calculator to turn those sizes into real-world transfer estimates.
❓ Frequently Asked Questions
Why does my 1 TB hard drive only show about 931 GB?
Because drive makers count in decimal (1 TB = 1,000,000,000,000 bytes) while Windows counts in binary (1 GB = 1,073,741,824 bytes). The physical capacity is identical — 1,000,000,000,000 bytes — but dividing by 1,073,741,824 gives about 931 GB. Nothing is missing; the two systems just use different-sized units with the same names. This converter shows both columns side by side so the difference is obvious.
What is the difference between decimal (SI) and binary (IEC) units?
Decimal (SI) units step by 1000: 1 KB = 1000 B, 1 MB = 1000 KB, and so on — used by storage manufacturers, networks, and most marketing. Binary (IEC) units step by 1024 and are correctly written KiB, MiB, GiB: 1 KiB = 1024 B. Operating systems historically label binary values with the decimal names (KB, MB, GB), which is the root of the confusion.
How many bits are in a byte?
One byte is 8 bits. That holds in both the decimal and binary systems — the 1000-vs-1024 difference only applies to the kilo/mega/giga prefixes, not to the bit-to-byte relationship. So an 8-bit value is exactly 1 byte, and a 100 MB file is 800 million bits (decimal).
Which system should I use?
Match the context. Buying or comparing drives, quoting network transfer sizes? Use decimal. Reading what your OS reports for free space or file size? That is usually binary. These are general estimates for planning and understanding — this tool converts exactly, but the labels a given device uses may differ.