Data Storage Converter

What this calculates

Enter a size in bits, bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, kibibytes, mebibytes, gibibytes, tebibytes or pebibytes, and this shows it in all twelve at once, with each conversion worked through. It also places the size on a scale running from a single byte to a petabyte, so a short text and a large drive can be read against each other.

Decimal units (kB to PB) and binary units (KiB to PiB) share their first letters but not their sizes, so each one is labelled decimal or binary. Every figure comes from exact definitions — nothing is converted with a rounded shortcut factor.

The formula

Every conversion goes through bytes: into bytes with one unit's size, then out again with another's.

The decimal units go up in powers of 1,000.

The binary units go up in powers of 1,024.

Because every factor is a whole number of bytes, or an eighth of one, a conversion is exact until it is rounded for display — and the calculator rounds each result once, from the exact figure.

Worked example

Going the other way, 1 TiB is 1,099,511,627,776 B, which is 1.099512 TB: a binary unit is always the larger of its pair.

Within one family the steps are exact. 1,000 MB is exactly 1 GB, and 1,024 MiB is exactly 1 GiB.

When to use it, and the mistakes to avoid

Use it when a storage size, a file size or a transfer allowance is given in a unit you do not think in, when two figures for the same size do not match and you want to know why, and when a figure is given in bits and you want it in bytes, or the other way round.

The mistakes that cost the most:

• Treating GB and GiB as the same. 1 TB is 1,000 GB but 931.3226 GiB, and 2 TB is 1,862.645 GiB. When the same size is shown in both, the binary figure is smaller because each binary unit holds more bytes — no space has gone anywhere. Check which unit a figure is in before comparing it with another.
• Mixing up bits and bytes. A byte is 8 bits, so a figure in bits is eight times the same figure in bytes. A lowercase b usually means bits and an uppercase B bytes: 100 Mb (megabits) is 100,000,000 bits, which is 12.5 MB, not 100 MB.
• Expecting the gap to stay the same size. It grows at every step, because each binary unit multiplies by 1,024 where the decimal one multiplies by 1,000. 1 KiB is 1.024 kB — 2.4% more — but 1 MiB is 1.048576 MB, 1 GiB is 1.073742 GB, 1 TiB is 1.099512 TB and 1 PiB is 1.1259 PB. So 1 TB is only 0.9094947 TiB.
• Expecting every digit of every result. Results are shown to seven significant figures — 1 GiB shows as 1.073742 GB — while the working keeps the exact byte figure. A size far too small for a unit, such as a thousandth of a bit in terabytes, petabytes, tebibytes or pebibytes, reads as 0, and a note under the result says so rather than leaving a silent zero.
• Entering a negative size. A size cannot be less than zero, so the calculator refuses one with a message instead of converting it.

FAQ