How many kilometers is it from Calais, France to Delhi, India?

As well, anyone have any ideas on the most direct route? We have to stop in Dusseldorf, Germany, so we're thinking FRANCE-BELGIUM-GERMANY-AUSTRIA-HUNGARY-R… (the border)-BULGARIA-TURKEY-IRAN-PAKISTAN-IN… ... anyone have an estimate on the distance? Or know a website that can calculate this?