Data Storage Converter
Convert between bits, bytes, KB, MB, GB, and TB — with a toggle for decimal (1000-based) vs binary (1024-based) units.
Decimal vs binary — why storage sizes never quite match
Hard drive and SSD manufacturers advertise capacity using decimal units, where 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, and so on. Operating systems, however, often report file and drive sizes using binary units, where 1 KiB = 1,024 bytes. This mismatch is why a drive labelled '1 TB' shows up as roughly 931 GB in Windows, which reports binary values with GB labels — no storage is missing, it's just measured with a different definition of the unit. macOS and many Linux tools report decimal units and show the same drive as 1 TB.
Worked example
1 decimal gigabyte (GB) = 1,000 megabytes (MB). But 1 binary gibibyte (GiB) = 1,024 mebibytes (MiB) — the same nominal 'GB to MB' conversion gives a different number depending on which system you're using, which is why this calculator lets you pick.
Converting a 1 TB drive to the size Windows shows
The unit system applies to both sides of a conversion, so this takes two steps. In decimal mode, convert 1 TB to bytes and you get 1,000,000,000,000 bytes. Switch to binary mode, enter that number of bytes and convert to GB (shown as Gibibytes, GiB), and the result is 931.322575 GiB. Windows labels that as 931 GB.
Estimating a download time
A 2 GB file is 16,000,000,000 bits in decimal mode. On a 50 Mbps connection, which moves 50,000,000 bits per second, that is 16,000,000,000 ÷ 50,000,000 = 320 seconds, about 5 minutes 20 seconds. Going the other way, 100,000,000 bits is 12.5 MB, so a 100 Mbps link tops out near 12.5 MB per second. Real downloads are slower because of protocol overhead, congestion and server limits.
Unit names and limits of this tool
- A lowercase b means bits and an uppercase B means bytes, so Mb and MB are eight times apart.
- The units run from bits to terabytes, with no petabytes and no per-second rates.
- Changing the unit system keeps your From and To choices, but KB, MB, GB and TB then mean KiB, MiB, GiB and TiB. Read the unit name in the result line.
- The result is rounded to six decimal places, so a very small amount in a very large unit, such as one bit in terabytes, shows as 0.
Frequently asked questions
Which mode should I use?
Use decimal if you're comparing manufacturer-advertised storage capacity (hard drives, SSDs, USB sticks). Use binary if you're checking a size reported by Windows, which shows binary-based values with KB/MB/GB labels. macOS and some Linux file managers report decimal sizes instead, so check which your system uses.
Is a bit the same as a byte?
No — 8 bits make 1 byte. Bits are typically used for network/internet speeds (megabits per second, Mbps), while bytes are used for file and storage sizes (megabytes, MB) — mixing the two up is a common source of confusion when checking download speeds against file sizes.
Can I convert directly between decimal and binary units, like TB to GiB?
Not in one step, because the unit system is applied to both sides. Convert to bytes in one mode, then enter the byte count in the other mode and choose the unit you want.
How do I convert internet speed in Mbps to megabytes per second?
Divide the megabit figure by 8, since there are 8 bits in a byte. 100 Mbps is 12.5 megabytes per second at best. The tool converts sizes only, so you apply the per-second part yourself.
Why does a tiny value show as 0?
Results are rounded to six decimal places. A single bit expressed in terabytes is smaller than that, so it displays as 0. Convert to a smaller unit, such as bytes, to see it.