Data Size Converter

Formula

Everything is stored in bytes:

Decimal prefixes use powers of 1000 ($\text{KB} = 10^3$, $\text{MB} = 10^6$, $\text{GB} = 10^9$, $\text{TB} = 10^{12}$). Binary prefixes use powers of 1024 ($\text{KiB} = 2^{10}$, $\text{MiB} = 2^{20}$, $\text{GiB} = 2^{30}$, $\text{TiB} = 2^{40}$). One byte is 8 bits.

Worked example

A phone advertised as 256 GB.

• Bytes: $256 \times 10^9 = 256{,}000{,}000{,}000$.
• In GiB: $256 \times 10^9 / 2^{30} = 238.42$ GiB.
• Difference: 17.6 gigabytes of marketing arithmetic, before the operating system takes its share.

The gap grows with every prefix step: about 2.4% at KB, 4.9% at MB, 7.4% at GB and 10% at TB.

Common mistakes

• Reading Mb as MB, which makes a download seem eight times faster or slower than it is.
• Expecting 1 GB = 1024 MB on a storage label. Storage makers use 1000.
• Assuming the shortfall in a new drive is a defect.
• Counting file sizes shown in different tools without checking whether they use 1000 or 1024.