1 kilobyte is precisely 1000 bytes

Published on 11/01/2026
Updated on 15/01/2026

• #opinion

When it comes to computer memory, we usually learn that a kilobyte is 1024 bytes, a megabyte is 1024 kilobytes, and so on. But what if I told you that it's not necessarily true and 1 kilobyte can be 1000 bytes? And what's more, this makes even more sense.

Table of contents

1. Why do we often say 1 kilobyte = 1024 bytes?
2. Why does 1000 still make more sense?
   1. What are the standard units?
3. Conclusion

Why do we often say 1 kilobyte = 1024 bytes?

Since computers work in a binary system (base 2), the memory is also addressed in binary. This means it's quite impractical to use memory addresses or produce RAM sticks with memory amounts that are not multiples of powers of 2. From the powers of 2 we chose 1024 (210) as the base order of magnitude, since it's very close to 1000 (2.4% difference) and it's not insanely large. So, in practice we often consider kilo as 1024 (210), mega as 1048576 (220), giga as 1073741824 (230), etc.

Why does 1000 still make more sense?

While binary kilo, mega and giga units are close to their decimal counterparts, some might already notice that the larger are the units, the more is the proportional inaccuracy. In order to illustrate, let's increase the units:

Unit	Decimal value	Binary value	Relative difference
Kilo	1000	1024	2.4%
Mega	1000000	1048576	≈ 4.8%
Giga	1000000000	1073741824	≈ 7.3%
Tera	1000000000000	1099511627776	≈ 10%
Peta	1015	~ 1.126 * 1015	≈ 12.6%
Exa	1018	~ 1.153 * 1018	≈ 15.3%
Zetta	1021	~ 1.181 * 1021	≈ 18.1%
Yotta	1024	~ 1.209 * 1024	≈ 20.9%
Ronna	1027	~ 1.238 * 1027	≈ 23.8%
Quetta	1030	~ 1.268 * 1030	≈ 26.8%

For 1 quettabyte the inaccuracy is already larger than a quarter. Even for 1 terabyte the difference is noticeable, around 10%. This problem often happens when hardware manufacturers (such as HDD or SSD) advertise the memory capacity in decimal units while the operating system might show in binary units.

Missing 70 gigabytes

For smaller amounts of memory the binary representation is pretty close to the decimal one, but diverges for huge amounts of memory.

What are the standard units?

This "kilobyte = 1024 bytes" rule is actually an old (often confusing) convention. In the tech industry there is still huge inertia, this old convention is still used by RAM manufacturers (JEDEC), tons of software and some operating systems (such as Windows). Interestingly, storage vendors often prefer the decimal convention, which creates even more confusion (mentioned above).

In order to solve this confusion, International Electrotechnical Commission introduced binary prefixes for binary units:

Binary units (International Electrotechnical Commission)	Decimal units (International System of Units)
Unit	Value
---	---
KiB (kibibyte)	10241
MiB (mebibyte)	10242
GiB (gibibyte)	10243
TiB (tebibyte)	10244
PiB (pebibyte)	10245
EiB (exbibyte)	10246
ZiB (zebibyte)	10247
YiB (yobibyte)	10248
RiB (robibyte)	10249
QiB (quebibyte)	102410

The guidance is: SI prefixes are powers of 10 only, and if you mean powers of 2 you should use IEC binary prefixes (Ki, Mi, Gi, …).

Conclusion

There is still a lot of inertia to equate 1 kilobyte to 1024 bytes. While this is usually acceptable depending on the context, it can sometimes cause confusion, especially for non-technical people.