Convert Farenheit to Celcius - vpjuslin/openhab GitHub Wiki
The example can be used to convert a fahrenheit temperature value to celcius:
import org.openhab.core.library.types.*
import org.openhab.core.persistence.*
import org.openhab.model.script.actions.*
rule "Convert_Temp_EG"
when
Item ZwaveTemperatureEGF changed
then
var tempFahrenheit = (ZwaveTemperatureEGF.state as DecimalType).doubleValue
var tempCelsius = (tempFahrenheit - 32) * 5/9
postUpdate(ZwaveTemperatureEG, tempCelsius)
end