How to calculate volume in liters of oil tanker in eliptical shape. need to know the formula.?

If the tanker would be drawn, it would have an elliptical-cylindrical figure. 
To calculate the volume, you must calculate first the area of its base. 
Since it is an elliptical base, the formula for solving the area of an ellipse should be used. 

Area of ellipse = (pi)(ab) 

where a = half the length of the major axis of the ellipse 
b = half of the length of the minor axis of the ellipse.... 

After solving the area of the elliptical base....multiply it to its length (length of the cylindrical oil tanker) 

in formula... 

V = (A elliptical base) x (Length) 

The units may be in cu. meter, cu. centimeter, cubic feet, etc...not in Liters... 

1 cu. m = 1000 L 
1 cu. cm = 1 ml = 1 x 10^-3 L 
1 cubic foot = 28.316846592 L 
1 cubic inch = 0.016387064 L 
1 cubic yard = 764.55485798 L