🔁 Conversion
MB, GB and TB Explained: Converting Digital Storage
How many megabytes are in a gigabyte? Learn how bits, bytes, KB, MB, GB and TB relate, why decimal and binary units differ, and how to convert between them.
Updated 2 November 2026 · 2 min read
Digital storage is measured in a ladder of units — bits, bytes, and then kilobytes, megabytes, gigabytes and terabytes, each a big step up from the last. Knowing how they relate helps you compare a phone's storage, a download size and a broadband allowance without second-guessing yourself.
Bits and bytes: the foundation
A bit is a single 0 or 1, the smallest unit of data. Eight bits make one byte, which is roughly the space one character of text takes up. Everything larger is built from bytes. A useful habit: storage (files, drives) is usually quoted in bytes, while internet and download speeds are quoted in bits — which is why a '100 Mbps' connection downloads at about 12.5 MB per second, not 100.
The ladder of units
Each step up the common ladder multiplies by 1,000:
To convert, multiply when you go down the ladder and divide when you go up. A 3,500 MB download is 3,500 ÷ 1,000 = 3.5 GB. A 0.75 GB app is 0.75 × 1,000 = 750 MB. The data storage converter does the steps for you and shows both the decimal and binary results side by side.
Why your drive looks smaller than the box says
There are actually two systems. Drive makers use decimal units based on powers of 1,000 (the KB, MB, GB above). Operating systems often measure in binary units based on powers of 1,024, now correctly labelled KiB, MiB and GiB (kibibyte, mebibyte, gibibyte):
- Decimal: 1 GB = 1,000,000,000 bytes.
- Binary: 1 GiB = 1,073,741,824 bytes (1,024 × 1,024 × 1,024).
A '1 TB' drive holds a trillion bytes, but your computer counting in binary reports it as about 931 GiB — nothing is missing, the two systems just count differently. The gap grows at larger sizes, which is why a new drive always looks a little smaller than advertised.
Quick reference
- A photo from a phone: roughly 2–5 MB.
- A standard-quality film: around 1–2 GB; in high definition, 4 GB or more.
- An hour of music streaming: about 50–150 MB depending on quality.
Data storage is one unit system among many you deal with daily. If you switch between measurement systems often, our metric vs imperial guide covers the same convert-by-multiplying logic for length, weight and volume.
Frequently asked questions
- How many MB are in a GB?
- In the decimal system drives use, 1 GB = 1,000 MB. In the binary system some operating systems use, 1 GiB = 1,024 MiB. For everyday conversions, 1,000 is the figure you'll usually want.
- What's the difference between MB and Mb?
- Capital B means bytes; lowercase b means bits, and there are 8 bits in a byte. File sizes use MB (megabytes); internet speeds use Mb (megabits), so a 100 Mb/s connection transfers about 12.5 MB each second.
- Why is KiB different from KB?
- KB (kilobyte) is 1,000 bytes; KiB (kibibyte) is 1,024 bytes. The binary KiB, MiB and GiB were introduced to remove the long-standing ambiguity over whether a 'kilobyte' meant 1,000 or 1,024 bytes.