Bytes Converter

KB, MB, GB and TB in both scales — decimal and binary — so you can see where the missing disk space went.

Conversion table

Size	In megabytes
0.5	500 MB
1	1,000 MB
1.5	1,500 MB
2	2,000 MB
2.5	2,500 MB
3	3,000 MB
4	4,000 MB
5	5,000 MB
6	6,000 MB
7	7,000 MB
8	8,000 MB
9	9,000 MB
10	10,000 MB
12	12,000 MB
15	15,000 MB

🔢 The two scales side by side

1 kB1,000 B — 1 KiB = 1,024 B
1 GB0.9313 GiB
1 TB (drive)931 GiB in Windows
16 GiB RAM17.18 GB decimal

Reading storage numbers correctly

Storage makers use decimal: a 1 TB drive holds a trillion bytes exactly. Windows divides by 1,024 three times and labels the result GB, which is where the 931 comes from.
macOS has counted in decimal since 2009, so the same drive reports about 1 TB there. Neither system is lying; they use different rulers.
RAM is always binary. A 16 GB memory module really is 16 GiB, or 17.18 billion bytes.
The IEC names are KiB, MiB and GiB, pronounced kibibyte, mebibyte and gibibyte. Ugly, but unambiguous.

Why one prefix ended up meaning two things

SI prefixes are powers of ten: kilo is a thousand, mega a million. Computers, addressing memory in binary, found 1,024 more natural than 1,000, and early engineers borrowed the SI names for it because the two were close. That approximation held while the numbers were small — a 2.4% gap at kilo — but it compounds: by terabyte the two scales differ by nearly 10%. The IEC settled it in 1998 by creating separate binary names, KiB, MiB and GiB, leaving kB, MB and GB to mean exactly what SI says.

Where the missing disk space went

Nowhere. A drive sold as 1 TB contains 1,000,000,000,000 bytes, which is what the box means and what regulators require. Windows then divides that by 1,024 three times to get 931.3, and labels it GB instead of GiB — so a correct number arrives with the wrong unit attached, and the difference looks like missing capacity. Formatting genuinely does cost a little, and the recovery partition costs a few gigabytes more, but the 69 GB everyone notices is purely a labelling mismatch between two counting systems.

Which scale applies where

Storage devices, network speeds and file transfer: decimal, powers of 1,000.
RAM and CPU caches: binary, always. A 16 GB stick is 16 GiB.
Windows and most Linux file managers: binary counting with decimal labels.
macOS since version 10.6 and Ubuntu since 10.10: decimal, matching the box.
Mobile data allowances: decimal, so a 5 GB plan is five billion bytes.
A byte is eight bits today, but early machines used six or nine, which is why formal standards say octet.

What things actually weigh

A page of plain text: 2–4 KB. This whole paragraph is under 300 bytes.
A phone photo: 3–6 MB; a RAW file from a camera, 25–50 MB.
A minute of MP3 at 192 kbps: about 1.4 MB.
An hour of 1080p streaming: roughly 3 GB; 4K, around 7 GB.
A modern video game: 50–150 GB, which is why download caps matter again.
A 1 TB drive holds roughly 250,000 phone photos or 50 4K films.

Worked examples

The two scales, side by side

A drive sold as 1 TB

1 TB = 1,000,000,000,000 bytes
÷ 1,024 three times = 931.32 GiB
Windows prints 931 GB, using the binary count with the decimal name

1 TB = 931 GiB, nothing is missing

16 GB of RAM

Memory is binary: 16 GiB
16 × 1,073,741,824 = 17,179,869,184 bytes
In decimal marketing terms that is 17.18 GB

16 GB RAM = 17.18 decimal GB

Frequently Asked Questions

Why does my 1 TB hard drive show only 931 GB?

Because two counting systems collide. The manufacturer sells a trillion bytes, which is 1 TB in decimal. Windows divides by 1,024 three times, arriving at 931.3, and then labels it GB instead of the correct GiB. No space is missing — the same bytes are being counted with a different-sized unit.

What is the difference between GB and GiB?

A gigabyte is 1,000,000,000 bytes; a gibibyte is 1,073,741,824 bytes, or 2 to the thirtieth. The gibibyte is about 7.4% larger. The IEC created the binary names in 1998 precisely so that GB could mean what SI says it means.

How many MB are in a GB?

1,000 in the decimal system used by storage makers and networks, and 1,024 in the binary system used for memory and by Windows' file manager. The question genuinely has two answers, which is why so much software disagrees with the box it came in.

Is RAM measured in binary or decimal?

Always binary. Memory is addressed by binary lines, so capacities come in powers of two by physical necessity: a 16 GB module is exactly 16 GiB, or 17,179,869,184 bytes. Storage has no such constraint, which is why drives are sold in round decimal numbers.

Why does my Mac show more free space than my Windows PC for the same drive?

Because macOS has reported decimal gigabytes since version 10.6 in 2009, matching the figure on the box, while Windows still counts in binary under a decimal label. The drive is identical; only the arithmetic on screen differs, and the gap grows with capacity — about 7% for a gigabyte and nearly 10% by a terabyte.

Is a byte always eight bits?

Today, yes, and that is why formal standards prefer the word octet for exactly eight. Early computers used six-bit and nine-bit bytes depending on their word size, and the eight-bit byte only became universal with the spread of IBM's System/360 architecture and, later, microprocessors.