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Data Size Converter

Convert between bytes, KB, MB, GB, TB and their binary counterparts KiB, MiB, GiB, TiB.

A 1 TB drive shows up as 931 GB in the operating system, and a 100 Mbps connection downloads at 12 MB/s — neither is short-changing anyone; two conventions are in play. Drive manufacturers use decimal SI (1 TB = 10^12 bytes) while operating systems use binary IEC (1 TiB = 2^40 bytes, about 1.0995 TB). This tool puts B, KB, MB, GB and TB alongside KiB, MiB, GiB and TiB so the difference is visible on the spot.

Two points of confusion. The M in a bandwidth figure is Mb (bits) rather than MB (bytes), and with 8 bits to a byte a 100 Mbps link peaks at 12.5 MB/s in theory. And memory sticks are labelled in binary (8 GiB) while drives are labelled in decimal (1 TB), so run the numbers here before buying storage if usable capacity matters.

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How to use

  1. Enter the size and its unit, decimal or binary.
  2. Read the value in all the other units.
  3. Note the decimal-versus-binary gap — 1 TB is about 931 GiB.
  4. Remember bandwidth is quoted in bits, not bytes.

How it works

Basic usage

Enter a value, pick the source and target units, and it converts live; the swap button reverses direction in one click.

Decimal vs. binary conventions

The decimal convention (GB/MB/KB) steps by 1000 — what drive and USB-stick makers label; the binary convention (GiB/MiB/KiB) steps by 1024 — what Windows and similar systems display.

Conversion examples

Example: 1 TB = 1000 GB, about 931 GiB under the binary convention; a 500 GB drive shows about 465.66 GiB usable.

Code example

JavaScript Two coefficient sets: SI and IEC 

const SI = { B: 1, KB: 1e3, MB: 1e6, GB: 1e9, TB: 1e12 };
const IEC = { B: 1, KiB: 2 ** 10, MiB: 2 ** 20, GiB: 2 ** 30, TiB: 2 ** 40 };

const conv = (v, T, f, t) => v * T[f] / T[t];

conv(1, SI, "TB", "GB");     // 1000 (decimal, exact)
conv(1, IEC, "TiB", "GiB");  // 1024 (binary, exact)
conv(1, SI, "TB", "TiB");    // 0.9095 (what a 1TB drive reports)

Python Bandwidth and download time 

mbps = 100                      # a 100 Mbps plan
mb_s = mbps / 8                 # 12.5 MB/s (bits to bytes)

file_gb = 1                     # a 1GB file (SI)
seconds = file_gb * 1e3 / mb_s  # 80 seconds

# Note: carriers quote M as Mb/s (bits); download tools show MB/s (bytes)

FAQ

Why does a 1 TB drive show only 931 GB?

The maker counts decimal: 1 TB = 1,000,000,000,000 bytes; Windows divides by 1024^3 for display: 1,000,000,000,000 / 1,073,741,824 is about 931 GiB. Capacity isn't missing — it's two conventions.

How fast is a 300 Mbps broadband download in MB/s?

300 megabits/s / 8 = 37.5 MB/s (note the 8x gap between bit and Byte, and the carrier's M means decimal Mb). The theoretical peak is 37.5 MB/s; real speeds run a bit lower due to line fluctuation.

GB or GiB — which should I use?

For drives, USB sticks and data plans use GB (decimal); for system memory and file-system-reported capacity, GiB is more accurate. This tool supports both — just pick the right unit.

What's the difference between bit and Byte (b vs. B)?

b means bit, B means Byte, and 1 Byte = 8 bit. Network bandwidth uses bit/s (like 100 Mbps), file sizes use Byte (like 100 MB) — divide by 8 to convert. This is the root of broadband speed and download speed often not matching.

1 TB equals how many GB?

Decimal: 1 TB = 1000 GB; binary: 1 TiB = 1024 GiB. Drive makers label decimal while operating systems display binary, so a 1 TB drive shows about 931 GB in the system. Both are correct — just different conventions.

What can 1 GB of mobile data do?

Rough magnitudes: about 1-2 hours of standard-definition video, 10-20 hours of online music, or hundreds of web pages. HD video is the biggest drain, reaching 1.5-3 GB per hour, so prefer WiFi for video.

Why do KiB and MiB exist?

Mixing decimal (KB = 1000 B) with binary (KiB = 1024 B) muddles capacity figures, so the IEC defined a binary prefix set — KiB, MiB, GiB — in 1998 to distinguish them. Systems now show binary values but still often label them GB, producing the illusion of "shrinking capacity."