Data Storage Converter

1. 1Type a value into any box — every other unit updates as you type.
2. 2Use the swap button to flip the two headline units.
3. 3Copy any result with the button beside it.
4. 4Adjust the decimal places if you need more or less precision.

There are two families of units here, and confusing them is why a 1 TB drive shows up as 931 GB. Decimal units — kB, MB, GB, TB — step in powers of 1,000 and are what storage manufacturers use. Binary units — KiB, MiB, GiB, TiB — step in powers of 1,024 and are what operating systems actually measure with.

The gap widens as the numbers grow: a kilobyte and a kibibyte differ by 2.4%, but a terabyte and a tebibyte differ by nearly 10%. Windows adds to the confusion by displaying binary quantities with decimal labels — what it calls 931 GB is really 931 GiB. Both families are listed here with their correct names so you can see exactly which is which.

Conversion works by taking your value to a single base unit and then out again, so every pair of units is consistent with every other. Values are calculated at full double precision and only rounded for display, which means round-tripping a number through two conversions returns what you started with.

Why a 1 TB drive shows as 931 GB

1. The manufacturer sells 1 TB = 1,000,000,000,000 bytes.
2. The operating system divides by 1,024 three times.
3. 1,000,000,000,000 ÷ 1,073,741,824 = 931.32

Result: 931 GiB — the same drive, measured with a different sized unit.

• Check whether a figure is decimal (GB) or binary (GiB) before comparing two numbers.
• Divide an internet speed in Mbps by 8 to get the most it can download in MB per second.
• Expect the free space on a new device to be lower than the box says; the system takes a share.
• RAM is sold in binary units, so 16 GB of memory really is 16 GiB.

• Why a 1 TB drive shows only 931 GB — and other storage numbers explained
• Mbps vs MB/s: how fast will my download really be?