MacStories, reviewing Convertible:

Convertible is one of the most peculiar and fun iPhone apps I’ve downloaded recently. On the surface, it’s a unit converter that uses “nested levels” to show conversions: levels start from the top with type (Length, Time, Currency, etc), then move to category (Metric, US & Imperial, Atomic, etc), and end with the actual unit you want to convert (Celsius, meters, Dollars, etc). The interaction is interesting: you can tap a level to bring up a list (therefore expanding the entire level), but you can also scroll horizontally to avoid taps. The animations are smooth and responsive. There are color schemes to choose from in the Settings, as well as an option to show or hide the iOS status bar.

I’ve thought about converter app UI for a long time. All of the alternatives on the App Store that I have tried are pretty much terrible, with the exception of Convertbot. Convertbot evokes a clear sense of care, but there was still an inherent clunkiness in use that I felt could be removed — I just failed to work out how.

However, today MacStories alerted me to Convertible and I was bowled over by its brilliance.

The funny thing is, Convertible isn’t new. In fact, relative to the lifetime of the App Store it is actually quite old. Somehow, I never found this gem in the App Store before.

It takes the UI metaphor of collapsible panels to the extreme. The interaction is similar to how folders work on the Home Screen. It’s even cleverer though; Convertible guides you through the necessary steps with its interface. The next step is the next panel downwards. Simple. Convertible avoids the default modal picker concept by using a non-modal sliding list. An ingenious little invention which removes even more UI complexity typically found in this category of applications. In the end, the computed result appears logically below the input; simultaneously straightforward and elegant.

Aside from the UI advances, there are some whimsical constants inbuilt that really trigger a smile. It is fun to convert lengths in terms of celebrities’ heights, or lengths of an Olympic swimming pool or whatever. Whilst these additions aren’t practical in any way, they trigger a sense of delight that any exemplar app should. It makes you want to keep it for when you do need it for something useful.

In my view, it’s the closest anyone has got to conversion app utopia on the iPhone to date. I recommend it wholeheartedly.