Bits vs Bytes: What's the Difference?

5 min read•June 1, 2026•Reviewed: June 1, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 1, 2026

A bit (binary digit) is the smallest unit of digital information — a single 0 or 1. A byte is 8 bits. That distinction might seem minor, but it has a major practical impact: your internet speed is measured in megabits per second (Mbps), while your file sizes are measured in megabytes (MB). Because there are 8 bits in a byte, a 100 Mbps connection downloads files at about 12.5 MB per second, not 100 MB per second.

Confusing bits and bytes leads to systematic misunderstanding of internet speeds, storage capacities, and data transfer times. This guide clears up the terminology and gives you the tools to translate between them correctly.

Bits: The Foundation

A bit is a single binary value — either 0 or 1. It is the fundamental unit of information in digital systems. Modern processors operate on groups of 8, 16, 32, or 64 bits simultaneously. All data in a computer — text, images, video, code — is ultimately represented as a sequence of bits. The bit was named and formalized by Claude Shannon in his 1948 information theory paper.

Bits are the native currency of digital communication. Network speeds (bandwidth) are expressed in bits per second because data travels as electrical or optical signals — streams of 0s and 1s. Units: bit (b), kilobit (Kb or Kbps for 'per second'), megabit (Mb or Mbps), gigabit (Gb or Gbps). Note the lowercase 'b' for bit vs uppercase 'B' for byte — though not everyone follows this convention consistently.

Bits, Bytes, and Network Conversion

1 byte = 8 bits
1 kilobit  (Kb)  = 1,000 bits
1 megabit  (Mb)  = 1,000,000 bits
1 gigabit  (Gb)  = 1,000,000,000 bits

Converting download speed to file size:
  100 Mbps ÷ 8 = 12.5 MB/s download speed
  1 Gbps ÷ 8   = 125 MB/s download speed
  25 Mbps ÷ 8  = 3.125 MB/s download speed

Time to download a 4 GB (4,000 MB) movie:
  25 Mbps:  4,000 ÷ 3.125 = 1,280 seconds ≈ 21 minutes
  100 Mbps: 4,000 ÷ 12.5  = 320 seconds ≈ 5 minutes
  1 Gbps:   4,000 ÷ 125   = 32 seconds

Bytes: Storage and File Sizes

The byte (8 bits) is the standard unit for file sizes and storage capacity. One byte can represent 256 different values (2⁸ = 256), enough to encode a single character of text in ASCII. A kilobyte (KB) is 1,000 bytes — about one page of plain text. A megabyte (MB) is 1,000,000 bytes — a few minutes of audio, or a few photos at low resolution. A gigabyte (GB) is 1,000,000,000 bytes — a typical movie file or a few hundred high-resolution photos.

Storage devices (hard drives, SSDs, flash drives) are measured and sold in bytes (KB, MB, GB, TB). RAM is measured in bytes (typically GB). File sizes your OS reports are in bytes. Network speeds your ISP advertises are in bits. This asymmetry — storage in bytes, speed in bits — is the primary source of confusion when people wonder why a '100 Mbps' internet plan does not deliver '100 MB per second' download speed.

Frequently Asked Questions

Why is my 100 Mbps internet not downloading at 100 MB/s?

Because internet speed is measured in megabits, not megabytes. 1 byte = 8 bits, so 100 Mbps ÷ 8 = 12.5 MB/s theoretical maximum. In practice, overhead from network protocols, congestion, and server limits typically reduce actual throughput to 8–11 MB/s on a 100 Mbps connection.

Is 'b' always bits and 'B' always bytes?

In formal notation: yes, lowercase 'b' = bit, uppercase 'B' = byte. So Mbps = megabits per second, MB/s = megabytes per second. However, informal usage is inconsistent — many apps, websites, and even ISPs use 'MB' when they mean 'Mb.' Always check context or do the ÷8 check to confirm.

How many bits is 1 GB?

1 GB = 1,000,000,000 bytes × 8 bits/byte = 8,000,000,000 bits = 8 gigabits (Gb). To transfer 1 GB over a 1 Gbps connection takes: 8 Gb ÷ 1 Gbps = 8 seconds (theoretically). A 1 TB drive stores 8,000 gigabits of data.

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