For iPhones, you have a lot more conversion options because it can also convert currency, which Androids don't do, and a host of other lesser common measurements like Nautical miles or Light years.

• Temperature: Fahrenheit to Celsius to kelvin

• Distance: km, cm, in, yard, nautical mile, foot, etc.

• Weight: Kg to pound, ounce, stone, etc.

• Currency: Pretty much any currency out there

• Angle: Degrees to radian, etc.

• Area: Acres to square foot, hectare, square kms, etc.

• Data: Bit to Megabyte, etc.

• Energy: kilocalorie, kilojoule, etc.

• Force: Newton, kilogram-force, etc.

• Feul: mile per gallon, kilometre per litre, etc.

• Length: Kilometre to mile, etc.

• Power: kilowatt to watt, horsepower, etc.

• Pressure: Atmosphere to pub, torr, etc.

• Speed: kilometre per hour to mile per hour, etc.

• Time: Minutes to hours, etc.

• Volume: cubic meter to gallon, fluid ounce, etc.

For Android phones, the options are more limited and based upon two-way conversions, the most commonly used ones:

• Fahrenheit to Celsius

• Centimetres to inches

• Kilograms to pounds

• Miles to Kilometres

• Galons to liters

• Kilobytes to Megabytes

• Meters per second to inches per second

• Seconds to hours

• Acres to Square meters

• Tip percentage, where you can see what X% of an amount is