Data Storage Unit Converter
Convert bytes, KB, MB, GB and TB — decimal and binary at once — and see how long that file actually takes to download.
Decimal (1000-based, how drives are sold and labelled)
Binary (1024-based, what Windows reports as "GB")
Download / Transfer Time Estimator
Best case at the full line rate. Mbps means megabits, not megabytes.
About this tool
Why "GB" doesn't always mean the same thing
Your hard drive box says 1 TB. Windows says you actually have about 931 GB. Nobody stole your storage — the drive manufacturer counted in decimal (1 TB = 1,000,000,000,000 bytes) and your operating system counted in binary (1 TiB = 1,099,511,627,776 bytes) but labeled it "GB" anyway. This converter shows both systems side by side at once, so you can see exactly why file sizes, download progress bars, and "available storage" numbers never quite line up.
How to use it
- Enter a value and pick its unit — anything from a single bit up to petabytes, decimal or binary.
- Every other unit updates instantly: decimal (KB, MB, GB, TB, PB — base 1000, the SI/marketing standard) in one grid, binary (KiB, MiB, GiB, TiB, PiB — base 1024, what your OS actually computes) in the other.
- Scroll down to the download/transfer time estimator, pick a connection speed (or enter your own in Mbps), and see how long that file size would actually take to transfer.
Decimal vs. binary, in plain terms
- Decimal (KB/MB/GB/TB, base 1000): Used by hard drive and SSD manufacturers, and by most network speed specs. 1 KB = 1,000 bytes.
- Binary (KiB/MiB/GiB/TiB, base 1024): Used internally by operating systems like Windows and by RAM specs, since computers work in powers of two. 1 KiB = 1,024 bytes. Windows actually calculates in binary but mislabels the units as KB/MB/GB instead of the technically correct KiB/MiB/GiB — that's the entire source of the "missing storage" confusion.
Real-world use cases
- Explaining the drive-size gap: Figure out exactly why your "1 TB" drive shows up as 931 GB in File Explorer or Finder.
- Estimating download times: Before downloading a large game, ISO, or dataset, see roughly how long it'll take at your actual internet speed.
- Sizing cloud storage or backups: Convert between the units cloud providers bill in (usually decimal GB/TB) and what your OS reports (binary), so your storage plan actually fits your files.
- Working with bit-rate specs: Convert a file size in bytes to bits (or back) when comparing against a network speed quoted in Mbps/Gbps.
Frequently asked questions
Why does my "500 GB" drive show less than 500 GB of usable space?
Two separate effects stack up: the decimal-vs-binary counting difference (roughly a 7% gap at the GB tier, larger at TB) plus space actually used by the filesystem itself and any pre-installed recovery partitions.
What's the difference between Mb and MB?
Lowercase "b" means bits, uppercase "B" means bytes, and there are 8 bits in a byte. A "100 Mbps" internet connection is 100 megabits per second, which is only 12.5 megabytes per second — a common point of confusion this converter's transfer-time estimator accounts for automatically.
Which unit should I use, decimal or binary?
For everyday comparisons (buying storage, understanding download sizes) either works as long as you're consistent. For anything technical — RAM specs, low-level programming, filesystem math — binary (KiB/MiB/GiB) is the mathematically correct choice since memory addressing is inherently a power of two.
How accurate is the download time estimate?
It's a straightforward calculation from file size and your stated connection speed, assuming you get the full advertised speed with no overhead. Real-world downloads are usually somewhat slower due to server limits, network congestion, and protocol overhead, so treat it as a best-case estimate.