There are quite a few conversion tools in the App Store. They all work to some degree, providing accurate conversions of different units of measure. However, while technically sound calculations are important, so too is a good interface and intuitive design so that users will actually want to use the app when they need a quick conversion. That's why Amount is such an impressive app -- managing to provide both of these much-needed components for a conversion app.
Amount opens with a calculator for you to enter a number of your choice. You are then given a menu of different measurement types. Each of them shows in subtitle how many options there are for conversion -- most have between five and 15. Tap any of these and a list of all conversions is shown for that number (using the base or most common unit). You can then tap any of the units listed on the page to switch the base measurement to that unit. So if you choose 100 and go to measurements of length, you can tap the "centimeters" button to change from the default meters that it selects.
The result is that it takes only seconds to find a conversion for any unit. Because all units are clearly marked, you are only two taps away from any single conversion. Changing the number you selected when opening the app is easy and manipulating the menus to find other conversions is immediately intuitive. If you are looking for a conversion app that finally works and looks good, download Amount.