Kilobytes, Megabytes and Gigabytes — Network Data Rates

Size and speed use similar language but different systems of measurement

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Bits and bytes aren't the same thing — they're based on different computational systems. A bit is generally a single unit of information, represented as a binary value of zero or one. Eight of these bits create one byte.

Usage

You'll more likely work with bits with computer networking. Most networking protocols and speeds are represented in a standard unit of measurement called bits per second. Measurements use standard SI prefixes like kilo, mega, and giga such that 1,000 bits per second is equal to 1 kilobit per second. It's all base-10 math when you're counting bandwidth.

However, computer storage aggregates bits into bytes and it is these bytes that form the basic unit of measurement for things like hard-drive capacity. In a practical sense, the basic unit of measurement for storage are kilobytes such that 1 KB is equal to 1,024 bytes, and 1 MB equals 1,024 KB. Because a byte consists of 8 bits in the binary system (e.g., 2^10), you'll always increment by 1,024 units as you increase the kilo/mega/giga scale instead of the 1,000 units you'd increase if you were working in bits.

Why It Matters

In theory, information transfers from one location to another one bit at a time. A computer with a 64-bit processor can simultaneously transfer 64 bits — but it's still one bit at a time, it's just that the "pipe" contains 64 channels within it. For that reason, all data-throughput measures accrue in bits.

Computers don't work with information one bit at a time, though. Usually, it takes eight bits considered as a group (as one byte) to render the smallest intelligible fact to a computer. This byte represents 1,024 different possible values, depending on whether the bits within the sequence represent a zero or a one.

Although you can translate bits to bytes and vice versa, use bits to measure throughput and bytes to measure file size and avoid cross-comparing the two.

Therefore, because computers tend to think in bytes rather than in their constituent bits, a file on your hard drive is constituted in bytes and thus increasing an order of magnitude requires you to multiply by 1,024 instead of just 1,000.

Sample Conversions

Conversion of Bits and Bytes
Bit Kilobit Megabit Byte Kilobyte Megabyte
1 0.001 0.000001 0.125 0.000125 0.000000125
10 0.01 0.00001 1.25 0.00125 0.00000125
100 0.1 0.0001 12.5 0.0125 0.0000125
1000 1 0.001 125 0.125 0.000125
10000 10 0.01 1250 1.25 0.00125
100000 100 0.1 12500 12.5 0.0125
1000000 1000 1 12500 125 0.125
Bits and bytes generally aren't cross-comparable.

Put in practical terms, a 1-gigabit Ethernet connection will transfer a 125 MB file in one second. It'll take a 10-megabit Wi-Fi connection one minute and 40 seconds to effect the same transfer.

The interplay of bits and bytes in computer networking presents interesting math challenges given that they're working in both decimal and binary number systems.