Data Storage Converter

How do you convert data storage units?

Multiply by 1,000 for each step down to a smaller unit, or divide by 1,000 for each step up, because decimal (SI) data units grow in steps of 1,000: 1 KB = 1,000 bytes, 1 MB = 1,000 KB, 1 GB = 1,000 MB and 1 TB = 1,000 GB. All of them are built on the byte, which is 8 bits.

For example, a 4,700 MB DVD image is 4,700 ÷ 1,000 = 4.7 GB, and a 2 TB drive holds 2 × 1,000 = 2,000 GB. The MB to GB converter and GB to TB converter handle these steps for any value.

Decimal GB versus binary GiB

Operating systems and memory makers often count in powers of two. The IEC gives these binary units their own names: a kibibyte (KiB) is 1,024 bytes, a mebibyte (MiB) is 1,024 KiB and a gibibyte (GiB) is 1,024 MiB. One GiB is 1,073,741,824 bytes, about 7.37% more than one GB. Drive makers advertise in decimal units, while Windows reports binary values but labels them GB and TB. macOS has used decimal units since version 10.6, so the same drive shows its advertised size there.

Is a kilobyte 1,000 or 1,024 bytes?

By international standard, a kilobyte is 1,000 bytes and 1,024 bytes is a kibibyte (KiB), but software and memory makers used “KB” for 1,024 bytes for decades, so the meaning of KB, MB and GB still depends on who is counting. The gap starts small and grows with every step, as the table shows.

The IEC introduced the binary prefixes kibi, mebi, gibi and tebi in 1998 to end the ambiguity, and they now live in IEC 80000-13. The BIPM SI Brochure is explicit that the SI prefixes refer strictly to powers of 10 and should not be used for powers of 2. In practice, drive makers, network equipment and macOS use decimal units; Windows counts in binary but labels the result GB and TB; and RAM is built in powers of two and sold as GB. That is why a 1 TB drive shows about 931 “GB” in Windows, and why a GiB is 7.37% larger than a GB. The MB to GB converter uses decimal units, and the converter at the top of this page includes KiB, MiB, GiB and TiB for binary sizes. Powers of two themselves are easiest to see in base 2; the number system converter shows them.

Which data units are used where?

Bits describe speeds and bytes describe sizes: network links and bitrates are quoted in kilobits, megabits and gigabits per second, while files, memory and drives are measured in bytes and their multiples.

• Bits and kilobits: network speeds, audio bitrates such as 320 kbps MP3, and serial links. A lowercase b means bits.
• Bytes and kilobytes: text files, small images and memory addresses. An uppercase B means bytes; pick bits or bytes in the converter at the top of this page to switch between them.
• Megabytes: photos, songs, email attachment limits and mobile app sizes.
• Gigabytes: phone storage, RAM, mobile data plans and video files.
• Terabytes and petabytes: hard drives, backup systems, NAS arrays and data center capacity.
• GiB and MiB: Windows file sizes, RAM specifications, Linux tools and cloud virtual machine sizes, which are often quoted in binary units.

Data work often touches other bases and rates: the number system converter covers binary and hex, and the time converter turns a download time in seconds into minutes or hours.

Is there an SI unit for data?

No. The bit and the byte are not SI units; they are defined in the international standard IEC 80000-13, which also sets the symbols bit and B and the binary prefixes. The SI supplies only the decimal prefixes placed in front of them.

A bit (binary digit) is the smallest unit of information, a single 0 or 1. A byte is 8 bits; networking standards often call it an octet, because some early computers used bytes of other sizes. The SI prefix ladder then runs kilo (10³), mega (10⁶), giga (10⁹), tera (10¹²), peta (10¹⁵), exa (10¹⁸), zetta (10²¹) and yotta (10²⁴), and in 2022 the General Conference on Weights and Measures added ronna (10²⁷) and quetta (10³⁰). Strictly, the SI symbol for kilo is a lowercase k, so kB is the formal spelling of kilobyte, while a lowercase b always means bits and an uppercase B means bytes.

Bits also measure color depth. A 1,920 × 1,080 image stored at 24 bits (3 bytes) per pixel holds 6,220,800 bytes, about 6.22 MB, before compression; the pixel and screen converter covers the image dimensions side.