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Tampile temperature converter is a plugin designed to provide your visitors with an wasy conversion tool for temperature: fahrenheit, celsius rankin and kelevin. It is working as a widget so you don't need to make any changes to your theme files. It can be very simple installed from sidebar customization in your blog admin panel.

It is javascript based, so it will never refresh the page to show up results, and won't redirect your visitors if they use it. No need to worry about design, since it will import the title tags from your template.