mind your b’s and K’s: the arcane art of measuring download speeds

I’ve just upgraded to the 30 MB/s internet plan at Charter cable (and added HBO so we can watch Game of Thrones), so here’s the obligatory speedtest results.

It occurs to me that the units for download can be incredibly confusing. Charter advertises the download speed plan using units of Mbps. So, the question naturally arises, how long should it take to download something 18.3 GB in size? (and a related question, if I am downloading something at 300 KB/s, am I getting my max download speed?)

1 GB refers to a gigabyte (10^9 bytes) in this context, since we are talking about file sizes and network speeds. If we were talking about RAM, a GB would actually refer to a gibibyte. However, 1 Mb is a megabit (10^6 bits), not a megabyte (10^6 bytes), because of the small-case b. So 1 Mb is actually 1/8 MB (since there are 8 bits per byte).

So 18.3 GB downloading at 30 Mbps should require:

(size) / (speed) = (time)

(18.3 x 10^9 bytes) / ( (30 x 10^6 bits / sec) x (1 byte / 8 bits) = 18.3 x 10^9 * 8 / 30 x 10^6 = 4880 seconds = 81.3 minutes

Wolfram Alpha gets the answer right, too (and I like teh natural language query – very intuitive).

Now, suppose I’m rocking 300 KB/s according to a certain beta software download client. How am I really doing? The capital B means it is kilobytes, so that’s actually 300 x 10^3 x 8 = 2400 x 10^3 = 2400000 = 2.4 Mbps. Wait, what??

I’m only getting 1/10th my actual download speed for this??

This is why it’s important to do the math. Of course, the download speed may be limited by a lot of other factors, most notably how fast the server at the other end can deliver the data. I clocked almost 40 Mbps doing a speedtest with some local, low-ping server somewhere, but for downloading this big file I’m probably going a lot further and their server has a lot more to do than humor my ping requests. I guess I should be satisfied.

(But, I’m not. grrr….)

screwed again by Charter Cable?


I renewed my service with Charter last fall, drawn in by the promise of $400 rebate if I renewed the “triple play” service of voice, data, and cable TV. Its been months without my rebate arriving so I sent in a query to the helpful (until now) email contact, having learned the utter futility of having phone conversations with Charter’s customer service.

Here is my email to Charter customer service:


I am writing to inquire about the status of my $400 rebate for renewing my Charter service last year. I had signed up for a triple-play package with voice, internet, and television with a two-year contract, and was supposed to have received $400 credit. Kindly advise on the status of my rebate. Thank you.

name on account – XXXX
service address – XXXX
service phone – XXX

Aziz Poonawalla

Here is the infuriating reply:


Thank you for contacting us with your question, we’ll be happy to look into the status of your gift card. For future reference, and for a faster reply please send your inquiry to Umatter2Charter@chartercom.com.

After reviewing the order history on the account we don’t see a qualifying service order placed within the timeframe of the current gift card promotion period.

Unfortunately you do not qualify for the offer and will not receive a gift card.

If you have further questions please do not hesitate to contact us.

Thank you,

Steve Creameans | Social Media Communications Specialist
941 Charter Commons Drive, Town & Country, MO 63017

I am certain there must be some loophole I did not anticipate and which the person I spoke to when ordering mys ervice did not bother to alert me to. This is frustrating beyond measure. Unless Steve misunderstood my question and thought I *just* renewed? But if he looked up my account he will clearly see that I renewed last year. So the response makes no sense.

At this point I am basically resolved to switch to Verizon FIOS as soon as it is available. Unless Charter makes good on this, this is really the last straw, no matter how attentive their social media folk are to blog posts or the twitter feed. Will update the post as I get further responses.