A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 1, posted (6 years 1 week 2 days 15 hours ago) and read 7069 times:
The large tanks used on British Tornado aircraft, IIRC, have a capacity of 2250 liters. A smaller one of 1500 liters exists, this is used by German and probably Italian aircraft.
One liter of jet fuel weighs about 0.8kg, add the weight of the tank itself and IMHO then the total weight should be about 1kg per liter of capacity.