Statical stability curve. (GZ curve)

Minimum stability requirements (as to the date)

Having a positive GM value alone is not sufficient.

 The minimum stability criteria for cargo ships as per the Load Line Convention

1. The area under the curve of righting lever (GZ curve) shall be not less than, 
1. 0.055 meter radians up to an angle of 30°
2. 0.09 meter radians up to an angle of 40° or the angle at which lower edges of any openings in the hull,superstructure or deck house which cannot be closed watertight, are immersed if that angle be less
3. 0.03 meter radians between 30° and 40° or the angle referred above

  2. The righting lever (GZ) should be 0.20m at an angle of heel equal to greater than 30°.
  3. The maximum righting lever (GZ) should occur at an angle of heel not less than 30°.
  4. The transverse meta-centric (GM) height should not be less than 0.15m.

IMO recommended general criteria for cargo ships  (IS code 2008)

(The only difference from the Load line rules above is that the maximum righting lever should occur at angle of heel not less than 25°. Others are the same.)

1. The area under the curve of righting lever (GZ curve) shall be not less than, 
1. 0.055 meter radians up to an angle of 30°
2. 0.09 meter radians up to an angle of 40° or the angle of down flooding if that angle be less
3. 0.03 meter radians between 30° and 40° or the angle referred above
   

  2. The righting lever (GZ) should be 0.20m at an angle of heel equal to greater than 30°.
  3. The maximum righting lever (GZ) should occur at an angle of heel not less than 25°. If this is not practicable, an alternative criteria based on an equalant level of safety may be applied to the approval of the administaration.
  4. The transverse meta-centric (GM) height should not be less than 0.15m.