How much in petrol would it cost to drive from calais, france to budapest, hungary?

That's about 1000 miles, so if you managed 40 miles/gallon (depends on your car and driving style) that's about 25 gallons, which is about 114 litres, which @1.35/ltr is just over �150. That shortest route would take 14 hours continuous driving (without getting lost) and you'd need money for toll roads too.