What’s the Diff: Megabits and Megabytes

August 18th, 2016

Megabits vs. Megabytes

What is the difference between a megabit and a megabyte? The answer is obvious to computer people – it’s “a factor of eight,” since there are eight bits in a single byte. But there’s a lot more to the answer, too, involving how data moves, is stored, and the history of computing.

What are Megabits?

“Megabit” is a term we use most often when talking about the speed of our Internet connection. Megabits per second, or Mbps, is a measurement of data transfer speed. 1 Mbps is 1 million bits per second.

Take Internet service providers, for example. My cable provider has upped my maximum download speed from 25 to 75 to 150 Mbps over the years. Fiber optic connections (Verizon’s FIOS, Google Fiber) can be much faster, where you can get the service.

What is a Megabyte?

“Megabyte” is a measurement most often used to describe both hard drive space and memory storage capacity, though the term of art we throw around most frequently these days is the next order of magnitude, the Gigabyte (GB). My computer has 8 GB of RAM, for example, and 512 GB of storage capacity.

How to Measure Megabits and Megabytes

A bit is a single piece of information, expressed at its most elementary in the computer as a binary 0 or 1. Bits are organized into units of data eight digits long – that is a byte. Kilobytes, megabytes, gigabytes, terabytes, petabytes – each unit of measurement is 1,000 times the size before it.

So why does network bandwidth get measured in megabits, while storage gets measured in megabytes? There are a lot of theories and expositions about why. I haven’t found a “hard” answer yet, but the most reasonable explanation I’ve heard from networking engineers is that it’s because a bit is the lowest common denominator, if you will – the smallest meaningful unit of measurement to understand network transfer speed. As in bits per second. It’s like measuring the flow rate of the plumbing in your house.

As to why data is assembled in bytes, Wikipedia cites the popularity of IBM’s System/360 as one likely reason: The computer used a then-novel eight-bit data format. IBM defined computing for a generation of engineers, so it’s the standard that moved forward. The old marketing adage was, “No one ever got fired for buying IBM.”

Plausible? Absolutely. Is it the only reason? Well, Wikipedia presents an authoritative case. You’ll find a lot of conjecture but few hard answers if you look elsewhere on the Internet.

Which means aliens are behind it all, as far as I’m concerned.

What Does It All Mean

Anyway, here we stand today, with the delineation clear: Bandwidth is measured in bits, storage capacity in bytes. Simple, but what can be confusing is when we mix the two. Let’s say your network upload speed is 8 Mbps (megabits per second), that means that the absolute most you can upload is 1 MB (megabyte) of data from your hard drive per second. Megabits versus Megabytes, remember to keep the distinction in your head as you see how fast data moves over your network or to the Internet.

Peter Cohen
Peter will never give you up, never let you down, never run around or desert you. He also manages the Backblaze blog.

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  • jp

    wait you guys actually do the 1000 times. i guess it makes sense as you guys deal with hdd and there marketing team uses it but each is 1024 times the size before it in practice for almost everything but data storage

  • wmbb

    Hello Peter,
    Here is a suggestion : one thing that Backblaze could do is add a way for Windows users to get the same storage measure that Windows displays in the folder properties and the size that Backblaze displays.
    Backblaze uses “MB basis 1000” for computing file and folder sizes. Windows doesn’t (I know they are wrong, but I don’t care in this case!). So anyway these differences are causing much headaches for your Windows customers when this could easily be solved by you (you can display automatically both measures) !
    Thanks in advance ;)

  • GlueFactoryBJJ

    Another issue with data transfer rates is, to one degree or another, the issue of parity and address/transmission headers. Since data transfers include parity bits (often on a per byte basis) and checksums in many protocols, in addition to the addressing headers, your real world DATA transfers (actual bytes of storage) are frequently <1/10 of the Mbps rating. So if you have a 100Mbps (100 megaBITS/sec) connection, then you will probably average something less than 10MBps (10 megaBYTES/sec) of actual data transfer rate… as a general rule of thumb. Anything above that is just gravy.

    • Surely! A bit different than raw transmission rate, which is the reason behind bandwidth’s measurement in bits, but something a lot of folks – including IT pros – forget about when they try to calculate transfer speeds.

  • SteveBlowJobsSucksDickInHell

    crApple loving hipster douche. Backblaze was better when you weren’t here.

  • A topic that causes a lot of confusion among non-techy people
    Nicely explained. :)