You can use the Convert function to convert a measurement from one set of units to another. The Convert function converts between units that measure the same type of thing (distance, area, time, temperature, and so on). 

To use Convert, you must specify the units from which to convert and to which to convert. You use the TConvType type to identify the units of measurement. 

For example, this converts a temperature from degrees Fahrenheit to degrees Kelvin:

TempInKelvin := Convert(StrToFloat(Edit1.Text), tuFahrenheit, tuKelvin);

TempInKelvin = Convert(StrToFloat(Edit1->Text), tuFahrenheit, tuKelvin);

You can also use the Convert function to perform more complex conversions between the ratio of two measurement types. Examples of when you might need to use this this are when converting miles per hour to meters per minute for calculating speed or when converting gallons per minute to liters per hour for calculating flow. 

For example, the following call converts miles per gallon to kilometers per liter:

nKPL := Convert(StrToFloat(Edit1.Text), duMiles, vuGallons, duKilometers, vuLiter);

double nKPL = Convert(StrToFloat(Edit1.Text), duMiles, vuGallons, duKilometers, vuLiter);

The units you're converting must be in the same conversion family (they must measure the same thing). If the units are not compatible, Convert raises an EConversionError exception. You can check whether two TConvType values are in the same conversion family by calling CompatibleConversionTypes. 

The StdConvs unit defines several families of TConvType values.