Data Storage Converter

Ask two people how many bytes are in a kilobyte and you can get two answers: 1,000 or 1,024. Both have been right at different times. The SI prefix "kilo" has meant exactly 1,000 since the metric system was born, but early programmers borrowed it for the nearest tidy power of two — 2¹⁰ = 1,024 — because memory is addressed in binary. For decades "KB" quietly meant both, and that ambiguity compounds at every tier: by the gigabyte the two readings differ by 7.37%, and by the exabyte by more than 15%. In 1998 the International Electrotechnical Commission ended the guessing with a second set of prefixes — kibi, mebi, gibi, tebi, pebi and exbi (KiB, MiB, GiB, TiB, PiB, EiB) — reserved strictly for the powers of 1,024, leaving kB, MB, GB and the rest for the powers of 1,000. This converter is built around that split instead of papering over it, which is the one thing most storage widgets get wrong: they collapse both systems into a single "KB" picker and silently pick one.

Every conversion here pivots through a single base unit: the byte. You enter an amount in any of the 14 supported units, the tool multiplies by that unit's bytes-per-unit factor to reach bytes, then divides by the target unit's factor to land where you want. Those factors are exact, not engineering roundings — the decimal units are powers of ten (1 kB = 1,000 B, 1 MB = 1,000,000 B, up to 1 EB = 10¹⁸ B), the binary units are powers of two (1 KiB = 1,024 B, 1 MiB = 1,048,576 B, up to 1 EiB = 1,152,921,504,606,846,976 B = 2⁶⁰), and 1 byte is exactly 8 bits by definition. All of them are exactly representable in the IEEE-754 doubles the calculator runs on, so there is no rounding drift hiding in the result.

The distinction the converter exists to protect is decimal versus binary. A decimal unit uses SI prefixes and scales by 1,000: this is what drive and flash manufacturers print on the box, so a "1 TB" disk holds exactly 1,000,000,000,000 bytes. A binary unit uses IEC prefixes and scales by 1,024: this is what RAM modules, file managers and most operating systems actually count in. The gap between the two is small at first and grows with every tier — a kibibyte is 2.4% bigger than a kilobyte, a mebibyte 4.86% bigger than a megabyte, a gibibyte 7.37% bigger than a gigabyte, a tebibyte 9.95% bigger than a terabyte, and an exbibyte 15.29% bigger than an exabyte. That widening gap is the whole "lost capacity" story: nothing is missing from your drive, the two rulers are just different lengths and the labels look identical.

One more axis matters: bits versus bytes. A byte is 8 bits, and the difference is not cosmetic — internet plans are sold in megabits per second (Mbps, lowercase b) while files download in megabytes (MB, uppercase B). A "100 Mbps" line moves 100,000,000 bits per second, which is 12,500,000 bytes per second, or 12.5 MB/s once you divide by 8. Getting the capital letter wrong is an eight-fold error, so this converter includes the bit as a first-class unit and keeps the byte/​bit boundary explicit.

What separates a serious data storage converter from a marketing widget is exactly this honesty: labelling the decimal and binary ladders as two distinct groups, using the correct capitalisation (lowercase kB for the SI kilobyte, capital KiB for the IEC kibibyte), and citing exact factors traceable to IEC 80000-13 and the NIST reference on binary prefixes rather than a hand-waved "about 1,000-ish". Get those right and the confusing questions — why a 1 TB drive shows 931 GB, why an 8 GB stick holds 7.45 GiB, why your download speed looks one-eighth of your plan — all answer themselves.

Every data storage conversion is one multiplication and one division through the byte. The general formula is:

where x is your input value, a(from) is the source unit's size in bytes, and a(to) is the target unit's size in bytes. To do it by hand, take the headline case — a "1 TB" drive shown by the operating system:

1. Look up the source-to-byte factor. A terabyte is decimal, so 1 TB = 1,000,000,000,000 bytes.

2. Multiply the input by that factor to get bytes. 1 × 1,000,000,000,000 = 1,000,000,000,000 bytes.

3. Look up the target-to-byte factor. Your OS counts in gibibytes, so 1 GiB = 1,073,741,824 bytes.

4. Divide the bytes by the target factor. 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB — the number Windows prints as "931 GB".

The same two steps work for any pair. Megabyte to mebibyte: 1 MB × 1,000,000 ÷ 1,048,576 = 0.95367431640625 MiB (exact). Gibibyte to gigabyte: 1 GiB × 1,073,741,824 ÷ 1,000,000,000 = 1.073741824 GB (exact). The bit is the one unit smaller than a byte: since 1 byte = 8 bits, converting bits to bytes is a divide-by-8, and converting a "100 Mbps" bandwidth to bytes per second is 100 × 1,000,000 ÷ 8 = 12,500,000 B/s = 12.5 MB/s.

To use this calculator, pick the source unit from the From dropdown and the target unit from the To dropdown — the units are grouped as bit/byte, decimal (kB…EB) and binary (KiB…EiB) so you can see which ladder you are on. Type a value and the result updates as you type. The default pair is GB → GiB, which surfaces the decimal-versus-binary gap the moment the page loads, and an all-units view lets you read one input against every other unit at once. Because every factor is exact, there is no rounding to configure; the only thing that changes between units is which power of 1,000 or 1,024 you divide by.