Data Storage Units: Bits, Bytes and Beyond
Every time you buy a phone, download a file, choose a cloud storage plan or check your internet speed, you are dealing with digital storage units. The terms bits, bytes, megabytes, gigabytes and terabytes get used constantly but are rarely explained clearly.
This guide explains every data storage unit from the smallest to the largest, shows you how to convert between them and links to the free Data Storage Converter for instant calculations.
The Fundamental Units: Bits and Bytes
| Bit (b) | The smallest unit of digital information. It has one of two states: 0 or 1. Everything in computing is built from sequences of bits. |
| Byte (B) | A group of 8 bits. The standard unit of storage for text and data. One byte can store one character of text. |
8 bits can represent 256 different combinations (2 to the power of 8 = 256). This is enough to encode all standard text characters. A capital letter A is stored as 01000001 in binary, which is the byte value 65.
The Data Storage Units in Order
| Unit | Size | Real World Scale |
|---|---|---|
| Bit (b) | 1 bit | Smallest possible unit |
| Byte (B) | 8 bits | One character of text |
| Kilobyte (KB) | 1,024 bytes | A short text email |
| Megabyte (MB) | 1,024 KB | A high quality photo (3 to 5 MB typical) |
| Gigabyte (GB) | 1,024 MB | A standard HD movie (1 to 2 GB) |
| Terabyte (TB) | 1,024 GB | A large hard drive (1 to 2 TB common) |
| Petabyte (PB) | 1,024 TB | Used by data centres and cloud services |
| Exabyte (EB) | 1,024 PB | The internet generates several exabytes of data per day |
Why 1,024 and Not 1,000?
Computers work in binary (base 2), so memory sizes are naturally powers of 2. The number 1,024 is 2 to the power of 10, the closest power of 2 to 1,000. This is why computer memory uses 1,024 as the multiplier rather than 1,000.
However, hard drive manufacturers and internet service providers often use 1,000 as the multiplier (the SI standard), which is why a 1 TB hard drive shows up as 931 GB on your computer. The drive is not faulty, the two different counting systems give different results for the same physical capacity.
Bits vs Bytes: A Common Confusion
Internet download speeds are measured in bits per second (bps) while file sizes are measured in bytes. You must divide by 8 to convert between them.
Download Speed Example
Your internet connection: 100 Mbps (megabits per second)
File size to download: 500 MB (megabytes)
Convert speed to megabytes per second: 100 Mbps divided by 8 = 12.5 MB per second
Time to download: 500 divided by 12.5 = 40 seconds
This is why a 100 Mbps connection does not download 100 MB per second.
Common File Sizes in the Real World
| One page of plain text | About 2 KB |
| A typical Word document (10 pages) | 100 to 500 KB |
| An email with no attachments | 20 to 100 KB |
| A compressed JPEG photo | 1 to 5 MB |
| An uncompressed RAW photo | 20 to 50 MB |
| A 3-minute MP3 song | 3 to 5 MB |
| A standard HD movie (1080p) | 1 to 5 GB |
| A 4K movie | 15 to 50 GB |
| A modern video game | 30 to 100 GB |
How to Convert Data Units
Data Conversion Examples
Convert 5.2 GB to MB: 5.2 multiplied by 1,024 = 5,324.8 MB
Convert 768 MB to GB: 768 divided by 1,024 = 0.75 GB
Convert 2 TB to GB: 2 multiplied by 1,024 = 2,048 GB
Related Tools
- Data Storage Converter bits, bytes, KB, MB, GB, TB, PB and more
- All Unit Converters browse all 74 converters on CalConvs
Frequently Asked Questions
Why is 1 TB not equal to 1,000 GB on my computer?
Hard drive manufacturers define 1 TB as 1,000 GB (using powers of 10), but your operating system measures storage using powers of 2 where 1 GB = 1,073,741,824 bytes. This means a 1 TB drive (1,000,000,000,000 bytes by the manufacturer) equals only 931.3 GB as shown by your computer. The drive is working correctly, the two definitions simply produce different numbers for the same storage capacity.
What is the difference between bits and bytes?
A bit (b, lowercase) is the smallest unit of digital data, with a value of either 0 or 1. A byte (B, uppercase) is 8 bits. File sizes are measured in bytes while internet speeds are measured in bits per second. To convert megabits per second to megabytes per second, divide by 8. This is why a 100 Mbps internet connection downloads files at about 12.5 MB per second, not 100 MB per second.
How many MB is a GB?
There are 1,024 megabytes in one gigabyte when using the binary definition used by computers. Some storage manufacturers and internet providers use 1,000 MB per GB (the decimal definition), which gives slightly different results. For most practical purposes, 1 GB equals approximately 1,000 MB.
Why does my internet speed show Mbps but file sizes show MB?
Internet speeds use bits (lowercase b) while file sizes use bytes (uppercase B). The two are related by a factor of 8, there are 8 bits in one byte. Always check whether a speed or size is expressed in bits or bytes. If your speed is 50 Mbps (megabits), your actual download rate is 50 divided by 8 = 6.25 MB per second (megabytes). This convention comes from telecommunications using bit rates and computing using byte-based file sizes.