Bits vs. bytes
“My internet connection is 100 Mbps (megabits per second), and my photo is 15 MB (megabytes) in size.”
Why does networking use bits, while computing and storage generally use bytes?
A bit is a unit of information: either a 1 or a 0.
A byte is 8 bits.
When we're talking about data processing and storage, bytes are convenient because computers generally organize and address data in byte-sized units. A file might be 15 MB, memory might contain 16 GB, and a CPU might operate on 64-bit words made up of 8-byte chunks.
Communications are different.
At the physical level, a network connection is fundamentally moving a stream of bits from one place to another. The natural measure of that signaling rate is therefore bits per second— 100 Mbps means 100 million bits per second.
So:
100 Mbps = 12.5 MB/s
in the theoretical, ideal case.
In reality, you won't necessarily transfer a 15 MB file in exactly 1.2 seconds because the network has protocol overhead, packet headers, error correction, encryption, retransmissions, and other inefficiencies.
The distinction is therefore less about what the data is and more about how we're measuring it:
Storage and processing → bytes
Communication and transmission → bits per second
A useful way to remember it:
Bytes describe the data. Bits describe the rate at which we're moving it.