💾 Data Storage Converter: Bytes, KB, MB, GB, TB and PB

What is the Data Storage Converter?

Digital storage starts with the bit, a single binary digit that is either 0 or 1. Eight bits form one byte, the smallest unit that typically holds one character of text such as the letter A. Four bits are sometimes called a nibble. Everything larger than a byte is just a multiple of the byte, but there are two competing ways to count those multiples, and that difference is the single biggest source of confusion when people convert storage units.

The decimal or SI system uses powers of 1000. One kilobyte is 1000 bytes, one megabyte is 1000 KB (1,000,000 bytes), one gigabyte is 1000 MB, one terabyte is 1000 GB, and one petabyte is 1000 TB. This is the system hard drive and SSD makers print on the box, the system used to quote network and internet speeds, and the system behind most marketing figures. It matches everyday intuition because the numbers stay round.

The binary or IEC system uses powers of 1024 and prefixes that end in "bi": 1 kibibyte (KiB) is 1024 bytes, 1 mebibyte (MiB) is 1024 KiB, 1 gibibyte (GiB) is 1024 MiB, and 1 tebibyte (TiB) is 1024 GiB. Computers work in binary and address memory in powers of two, and 1024 is the nearest power of two to 1000 (2 to the power 10). Operating systems such as Windows still display file and memory sizes using 1024 multiples while labelling them KB, MB or GB, which is exactly why a drive sold as 1 TB shows as about 931 GB in File Explorer. No space is missing; the two systems just count differently.

The gap between the two systems compounds at every step. At the kilobyte level the difference is only about 2.4 percent, but it grows to roughly 4.9 percent at mega, 7.4 percent at giga, and about 10 percent by the terabyte level. That is why a 500 GB SSD (decimal) usually reports as around 465 GiB inside Windows, and a 2 TB drive shows near 1.82 TiB. For small files the difference is trivial, but across a full drive it adds up to tens of gigabytes.

Knowing which unit you need depends on the job. Use decimal MB, GB and TB for drive capacity, cloud storage plans, bandwidth caps and any customer-facing figure. Use binary MiB, GiB and TiB for RAM, memory buffers, and the exact sizes your operating system reports. This converter keeps both systems side by side and clearly labelled, and it routes every calculation through a single base unit, the byte, so results stay consistent no matter which box you type into.

A related trap is confusing bits with bytes. Internet and network speeds are quoted in bits per second, while file sizes are quoted in bytes. Because there are 8 bits in a byte, a 100 megabit per second (Mbps) connection transfers about 12.5 megabytes (MB) per second at best, not 100 MB. Getting that factor of 8 right is essential for estimating real download times and data usage.

When to use it

• Checking how many MB are in a GB when comparing a phone or cloud storage plan.
• Working out why a 1 TB drive shows up as about 931 GB in Windows or macOS.
• Converting a raw file size from bytes to KB or MB for a quick sanity check.
• Estimating how many photos, songs or videos fit on a card of a given capacity.
• Translating a network speed in Mbps into how many MB per second you actually get.
• Sizing a backup or database export by converting between GB, TB and petabytes.

How to use the Data Storage Converter

1. Find the unit you already know in the decimal (SI) or binary (IEC) section.
2. Type your number into that box; leave the others blank.
3. Read the converted value from every other unit, which updates instantly.
4. Use the decimal section for drive, plan and network figures.
5. Use the binary section to match what your operating system reports on screen.

Formula & method

Worked examples

Decimal (SI) versus binary (IEC) units in bytes

Common decimal conversions

Rough real-world capacity (decimal units, approximate)

Common mistakes to avoid

• Mixing up bits and bytes. A byte is 8 bits. Internet speeds are usually in megabits per second (Mbps) while file sizes are in megabytes (MB). A 100 Mbps connection moves about 12.5 MB per second, not 100 MB, because you divide the bit figure by 8.
• Expecting a 1 TB drive to hold a full 1 TB as the OS counts it. Makers use decimal (1 TB = 1,000,000,000,000 bytes), but Windows divides by 1024 and still writes "GB". The same drive then reads as roughly 931 GB, so no space is missing, it is just counted differently.
• Assuming KB always means 1024 bytes. In decimal (SI) usage 1 KB = 1000 bytes. The 1024-byte unit has its own correct name, the kibibyte (KiB). Picking the wrong base adds about a 2.4 percent error per step, which compounds to roughly 10 percent by the terabyte level.
• Using a lowercase b and uppercase B as if they were the same. By convention a lowercase b means bits and an uppercase B means bytes. So Mb is megabits and MB is megabytes, an 8-fold difference. Reading Mbps as MBps overstates real transfer speed by eight times.
• Forgetting that reported free space is always less than the label. Formatting, the file system, and reserved space all consume capacity. Combined with the 1000 versus 1024 gap, a new 256 GB phone often shows around 230 to 240 GB usable, which is normal and not a defect.
• Converting across many steps by eye. Jumping from bytes straight to GB in your head invites slipped decimal places. Convert to the byte base first, then divide once by the target unit size, so a single calculation replaces several error-prone multiplications.

Glossary

Bit

The smallest unit of digital data, a single binary digit that is either 0 or 1. Written with a lowercase b.

Nibble

A group of 4 bits, or half a byte. It maps neatly to a single hexadecimal digit.

Byte

A group of 8 bits and the basic unit for measuring file and storage size. Written with an uppercase B.

Decimal (SI) units

Units based on powers of 1000, such as KB, MB, GB and TB. Used by storage makers and networks.

Binary (IEC) units

Units based on powers of 1024, with names like KiB, MiB, GiB and TiB, used to count exact memory sizes.

Kibibyte (KiB)

Exactly 1024 bytes. The binary counterpart to the 1000-byte kilobyte, standardised by the IEC.

Mbps

Megabits per second, a measure of data transfer speed. Divide by 8 to get megabytes (MB) per second.

Petabyte (PB)

One thousand terabytes in decimal units, or 1,000,000,000,000,000 bytes. Common in data centres and cloud storage.

Frequently asked questions