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My site shows trails and currently shows distance in km and elevation in m. US users don't like this and want to see things in miles and feet respectively.

Does anybody have any evidence for the best way to do this?

Options I can think of:

  • Show a link in the top right corner that switches from Metric to US Customary. Default to US Customary for showing trails in the US and Metric everywhere else. (Possibly show Imperial for UK trails.)
  • Show everything as x km (y mi) but switch to y mi (x km) for US trails. (Possibly allowing a switch at the top).

Is US Customary a good term? This is what Wikipedia uses. Maybe km/m and mi/ft?

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I think you probably meant something other than 'evidence'. May be you meant 'suggestion'. – Kris Dec 24 '11 at 6:49
up vote 1 down vote accepted

If users are registered, best option would be a one-time setting, available in the settings page. Once they've chosen which system to use they are probably not going to change it, so no problem if it is not inmediately available.

If they are not registered, you could use cookies or sessions to ask them on the first visit which system to use, and then maintain it as long as the cookie or session is there.

If neither are applicable, I always think simple is better: just put both X km (Y miles). Nothing is more inmediate than this.

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It would be hard to provide evidence for this. One idea is tracking the location of the user and defaulting to that.

Putting the switch in the top right corner cannot be wrong, any approach you take.

For naming, no need to be over specific. I would consider the words "Metric" and "US" or "Miles" clear enough.

You could complement it all with offering a mouse-over hint with the other unit system. Say hovering over a kilometer number hints the equivalence in miles.

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Some sites provide a simple switch for temperature in the weather report like this:

F° | C°

immediately following the temperature value.

Mouse-over highlights the current setting and clicking the other switches over.
I find this not only intuitive but very convenient.

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