Usage Based Billing or UBB has been a hot topic for Canadian Internet Users over the last six to eight weeks with hundreds of thousands of Canadians signing online petitions and complaining to their Member of Parliament.

In discussing UBB, the talk usually revolves bandwidth caps which are measured in Gigabytes but in talking to users, it’s clear there is some confusion about what exactly a Gigabyte is so our question today is "Is it a Gigabyte or a Gibibyte?"

Let’s start off by defining what a Gigabyte and a Gibibyte is and how they differ.

What is a Gigabyte?

The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means ten to the power of nine in the International System of Units (SI), therefore 1 gigabyte is a billion (1,000,000,000)  bytes. The unit symbol for the gigabyte is GB or Gbyte, but not Gb (lower case b) which is typically used for the gigabit.

Think of it this way
  • 1 Kilobyte (KB) = 1,000 bytes
  • 1 Megabyte (MB) = 1,000 x 1,000 or 1,000,000 bytes
  • 1 Gigabyte (GB) = 1,000 x 1,000 x 1,000 or 1,000,000,000 bytes.

If you were a Shaw Cable customer subscribing to the Shaw High Speed Internet package you would have a monthly transfer limit (aka bandwidth cap) of 60GB a month or 60 Billion bytes.

What is a Gibibyte?

Simply speaking a Gibibyte is a what computer scientists and programmers used to call a Gigabyte.

While the majority of the world deals in the base ten (0-9) decimal system for measurement, we must remember that the computer world deals in the binary or base two (0 and 1) system.

For a computer scientist prior to the 21st century, a kilobyte was not a thousand bytes rather it was defined as “2 to the power of ten (210)” or 1,024 bytes. The computer scientists used to define a megabyte as "2 to the power of 20" or 1,048,576 bytes and a Gigabyte as "2 to the power of 30" or 1,073,741,824 bytes.

Since a Gigabyte can’t be both 1,000,000,000 bytes and 1,073,741,824 bytes, the powers that regulate these matters needed to re-define what a Gigabyte was in order to eliminate confusion among the computer world and the rest of the world.

In the late 1990’s the Institute of Electrical and Electronics Engineers (IEEE) standardized on the International System of Units (SI) definition that GIGA was one billion units so a Gigabyte was defined a billion (1,000,000,000) bytes.
The binary interpretation of "2 to the power of 30" or 1,073,741,824 bytes became known as a GibiByte whose symbol is GiB.

Difference between a Gigabyte and a Gibibyte

In summary, a Gigabyte is 1,000,000,000 bytes while a Gibibyte is 1,073,741,824 bytes which means a Gigabyte is actually about 7% smaller than a Gibibyte.

If you’ve ever wondered why that 500GB hard drive you just bought shows only about 465 GB of free space after you format it, then you have seen a practical example of why it’s important to understand the difference between a Gigabyte and a Gibibyte.

Hard Drive manufacturers sell hard drives in Gigabytes but Microsoft Windows reports in Gibibytes but incorrectly uses the symbol GB instead of GiB.

Measuring Internet Usage

So why is knowing the difference between a Gigabyte and a Gibibyte matter when discussing your bandwidth cap?

The reason is that Canadian Internet Service Providers themselves don’t seem to understand the difference themselves and the result is many consumers are left wondering how their internet usage is being measured.

For example, on the support portion of the Rogers Cable website, the company answers the question “How can I calculate my additional usage and charges?” in this manner

The usage tool tracks your usage in megabytes. To convert your usage into gigabytes and calculate your additional charges, follow these steps:
1. Over usage = (“Total Usage” MINUS “Service Includes”) DIVIDED BY 1,024
2. Round down to the nearest gigabyte
3. Over-usage charge = Over usage in GB (from Step #1) MULTIPLIED BY $1.25
For example:
Total Usage: 128,522 MB
Service Includes: 90,000 MB
1. Over usage in GB = (128,522 – 90,000) / 1,024 = 37.62 GB
2. Round down to the nearest gigabyte = 37 GB
3. Over-usage charge = 37 X $1.25 = $46.25
By dividing Megabytes by 1,024 rather than 1,000, the Rogers calculation appears to be confusing Gigabytes with Gibibytes so the question becomes, if Rogers doesn’t know the difference, can consumers be confident the usage numbers being reported are accurate.

At Digital Home, we believe that Internet Service Providers who impose Internet Bandwidth caps and charge for overages should disclose, at a minimum, the following information:
  • How they measure internet traffic?
  • What Independent Verification system is in place to verify the accuracy of their internet bandwidth meters?
  • How they calculated overages?
  • Whether their bandwidth are truly in Gigabytes or Gibibytes?

Over the last month, Digital Home has asked many of Canada's top Internet Service Providers to clarify how Internet usage is measured and verified but, to date, has not received any response regarding their measurement methodologies and verification procedures.

Discuss Usage Based Billing and all of its ramifications in Digital Home’s Internet and Phone discussion forum .