udunits/src/main/java/ucar/units/ScaledUnit.java
public double toDerivedUnit(final double amount) throws ConversionException {
        if (!(_unit instanceof DerivableUnit)) {
            throw new ConversionException(this, getDerivedUnit());
        }
        return ((DerivableUnit) _unit).toDerivedUnit(amount * getScale());
    }
public double toDerivedUnit(final double amount) throws ConversionException {
        if (!(_unit instanceof DerivableUnit)) {
            throw new ConversionException(this, getDerivedUnit());
        }
        return ((DerivableUnit) _unit).toDerivedUnit(amount * getScale());
    }
Converts a numeric value from this unit to the underlying derived unit.

@param amount
The numeric value in this unit.
@return The equivalent value in the underlying derived unit.
@throws ConversionException
Can't convert value to the underlying derived unit.