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If you’ve ever been stumped by talk about megabytes and gigabytes, you’re not alone. This is a no-frills quick guide that’ll help you wrap your mind around understanding file sizes.

The smallest size is a byte

A byte is the smallest file size. It’s enough space to hold a single character.

Then, it’s like the decimal system

As you jump from one file size to the next, everything’s multiplied by 1,000. Well, 1,024 to be exact, but let’s stick with 1,000 for simplicity.

Here are the common file sizes from smallest to largest

  • 1 byte (B) = Single unit of space
  • 1 kilobyte (KB) = 1,000 bytes
  • 1 megabyte (MB) = 1,000 kilobytes
  • 1 gigabyte (GB) = 1,000 megabytes
  • 1 terabyte (TB) = 1,000 gigabytes
  • 1 petabyte (PB) = 1,000 gigabytes

Relatively, how big are each of these?

  • A single character can be held in a byte
  • A kilobyte can hold 1,000 characters, or a few paragraphs of text
  • The easiest way to think of megabytes is in terms of music or Word documents: A single 3-minute MP3 is usually about 3 megabytes; A 2-page Word document (just text) is about 20 KB, so 1 MB would hold about 50 of them.
  • Gigabytes, likely the size you’re most familiar with, are pretty big. They can hold about 300 MP3s or 50,000 Word docs.
  • Terabytes, which are becoming more popular as file sizes get bigger, are huge. A single TB would fit about 300,000 3-minute MP3s or 50,000,000 2-page Word documents.
  • Commercially-available drives haven’t even reached a petabyte yet. 1 PB would hold 300 million MP3s or 50 billion Word documents. That’s one intense essay.

Another quick comparison

Here’s a quick file size comparison (assuming these files are pretty typical):

  • A text file is tiny
  • A JPEG image is bigger
  • A song file (MP3) is bigger than that, a few megabytes
  • A RAW image file is bigger than a song
  • A low-resolution video is large
  • A high-resolution video is huge
  • An installation file for an operating system (e.g., Windows 10, Mac Mojave) is several GB (very large!)

Don’t mix up drive space and RAM!

When you’re buying a new computer or phone, you may notice that both drive space and RAM are likely measured in GB. That definitely doesn’t make them the same thing.

Pop over to my laptop buying guide for more on the difference between these two pieces of hardware.

How does this help grow my business?

Once you understand file sizes, it’s much easier to to a few things:

  1. Know how much data you can fit on your computer or phone
  2. Shop for a new computer or phone and better understand your needs
  3. Rapidly understand different file types and their relative sizes