Friday, 29 January 2010

Data Roaming Rates: What does it all mean?

The fancy new Phones, and now tablet PCs, offer 3G internet to your hand. All of which is very pretty until you need to travel, where you can expect your data costs to go from "very high" to "crippling". Telcos do tell you what these data rates are, in technical terms of so much per kilobyte and so forth.

Roaming data is incredibly convenient, but at 10c or 30c for each 10KB, it can be expensive. It's important to optimise your usage to avoid a shock when you see your bill. (For example, if your laptop conscientiously downloaded the latest 40MB Microsoft security update in the background without you realising, it could easily cost $1,200.)

-- Vodafone

Well, I can imagine.

The trouble is, normal people do not think in kilobytes.

One of the problems is that talk of megabytes and gigabytes is so much techno-gobbledygook for many consumers. They may have no idea what it translates into when it comes to web surfing, sharing videos, e-mail, downloading movies and music, or the many other functions that have made computers an indispensable tool of daily living.

So lets break it down using Vodafones own mean estimate of 2c a kilobyte, and working out typical per use activity costs:

  • email
    • plain text: $0.015
    • Internet average: $1.50
    • Warning: a typical email may contain pictures too (see below)
  • pictures
    • std photo: $26
    • hidgh-res: $100
  • music
    • $86 per song
  • movies
    • 3-min YouTube: $190
    • TVNZ Episode: $8,000
  • web surfing
    • average: $2.60 per page
    • page images: $0.24 each
    • animated ads: $2.00 each


Each keyboard character takes up 1 byte in plain text mode. A short message, about 100 words, would be around 500 bytes + the information used to get the mail to the right person and so forth. So budget 1kB per plain text email.

Rich text is a different story. Depending on the formatting you use, a RTF email can double in size. As well as which, most RTF mails have a plain text version copied to the end. So budget 3k for RTF.

World wide, the average email size is about 75kB. If you do a lot of large emails, you'd want to budget with this figure instead.

None of this include any pictures or special content people add to their emails.


If a picture is worth 1000 words, it is also 1000 times the sizeA 1 megapixel photo clocks in at 1.3Mb - . Higher resolutions are now common, and they are proportionally bigger with 5Mb per photo not uncommon. This is why photos taken with phone cameras are so small.


On my Box - Gin Wigmore's "Oh My" ripped to a 4.3MB vorbis file (at high fidelity). mp3 and ogg format songs are usually a bit more (mp3) or a bit less (ogg) than 1MB per minute.


A short film of the sort you'd find in YouTube is about 9-10MB, so we are thinking 3-10 times the size of a photo. This would be a clip about 2-3mins long. The higher the movie quality, the bigger it is. A full DVD movie is 4-6GB for 1.5 to 2hours. TVNZ Video On Demand episodes can be around 350-500Mb.

browsing the web

Browsing the web involves getting web pages, which can vary in size a great deal depending on what is on them.

If you turn all images, scripts and dynamic content off, the bare-bones html clocks in at 25k. Webmasters are pretty decent about images, normally, and do not use photo size pics. The little giff or png widgets, like the firefox link on this page (left) are only 1-2k, and main pictures are usually 12k. The total web average size of a page is 130kB. Fancy animated ads can slow a page down: they are usually short movie clips 2-3 seconds long - about 1.5MB


Careful though: these are approximate, back of an envelope, figures - I even approximated 1MB as 1000kB. Even so... global roaming does not look like such a good option for staying in touch. This is something you have if you travel a great deat on the company, and the company pays for it.

If you are going overseas in any other capacity, buy a local sim card and switch data roaming OFF. Use local wifi hotspots for data.

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