What is Data Storage Conversion?
Convert between bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes. Uses decimal (SI) prefixes: 1 KB = 1,000 B, 1 MB = 1,000 KB.
Supported units: Byte (B), Kilobyte (KB), Megabyte (MB), Gigabyte (GB), Terabyte (TB), Petabyte (PB).
Why "1 TB" drives always show as "931 GB"
Data storage has two incompatible systems that look almost identical, which is why most people have been confused at some point. The SI (decimal) system uses powers of 1,000: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 TB = 10¹². The IEC binary system (standardised in 1998) uses powers of 1,024 and prefixes like kibi-, mebi-, gibi-: 1 KiB = 1,024 B, 1 MiB = 2²⁰ B, 1 TiB = 2⁴⁰ B. Hard-drive manufacturers advertise in SI — a "1 TB" drive really has 10¹² bytes. Windows (and older macOS) displays in binary but still uses the letters KB/MB/GB/TB, so 10¹² bytes becomes "931 GB" on screen. That isn't the drive lying to you; it is the OS using different prefixes with the same letters. Modern macOS (since 10.6) and Linux generally follow the SI convention, matching what it says on the box.
Where storage conversion matters
Buying HDDs, SSDs, and flash drives
Advertised capacity is in SI decimal (1 TB = 10¹² bytes). Your OS may report the same drive as 931 GiB. Converting makes the "lost" 69 GB explainable rather than suspicious — it's a unit choice, not a defect.
Cloud storage and pricing
AWS S3, Google Cloud, and Azure bill by GB using the SI decimal prefix, while many tools (rclone, duplicity, etc.) report usage in GiB. The 7 % difference adds up on a petabyte-scale bill.
Network bandwidth
Internet plans are sold in bits per second (Mbps, Gbps). Downloads show in bytes per second (MB/s). A "1 Gbps" line delivers about 125 MB/s, not 1,000 — the ratio is 8:1 because there are 8 bits in a byte. Mixing them up produces complaints of "slow speed" that are actually mathematically correct.
Video, photo, and backup sizes
4K 10-bit video runs roughly 400–800 Mbps, filling a terabyte in about 3 hours. Camera RAW files are 20–80 MB each; estimating how many fit on a card or cloud tier requires confident unit conversion.
Databases, logs, and servers
Developers spec row sizes in bytes, table sizes in GB, and shard limits in TB. PostgreSQL's pg_size_pretty() returns binary-prefixed text, but billing dashboards use SI — keeping both in mind avoids nasty surprises in quota planning.
Common Conversions
- 1 Byte (B) = 0.001 Kilobyte (KB)
- 1 Byte (B) = 0.000001 Megabyte (MB)
- 1 Kilobyte (KB) = 1000 Byte (B)
- 1 Kilobyte (KB) = 0.001 Megabyte (MB)
- 1 Megabyte (MB) = 1000000 Byte (B)
- 1 Megabyte (MB) = 1000 Kilobyte (KB)
FAQ
Q: How many MB in 1 GB?
A: 1 GB = 1,000 MB (decimal/SI standard).
Q: How many GB in 1 TB?
A: 1 TB = 1,000 GB = 1,000,000 MB.
Q: How many bytes in 1 kilobyte?
A: 1 KB = 1,000 bytes (SI). Note: in binary (KiB) it is 1,024 bytes.
Q: Why does my 1 TB hard drive show as 931 GB in Windows?
A: The drive really holds 1,000,000,000,000 bytes (SI), but Windows labels with binary prefixes while keeping the same letters. 10¹² ÷ 2³⁰ ≈ 931, so what it calls "GB" is actually GiB. No data is missing.
Q: What is the difference between Mb and MB?
A: Lowercase "b" means bit, uppercase "B" means byte. 1 byte = 8 bits. Internet speeds use Mb (megabits), file sizes use MB (megabytes). A 100 Mbps link transfers about 12.5 MB per second.