The tsunami events caused by mega-earthquakes in the Indian Ocean (9.0, 12-26-04) and NE Japan (9.0, 03-11-11) had dramatic impact over extended areas and various distances from the source area, providing a huge amount of data, during unprecedented situations. The records of magnitude and grade of impact allowed a more precise specification of a more objective, 12-grade intensity scale of tsunamis, covering a full range of intensities, situations and environments. The proposed scale is based on 6 groups of criteria linking quantities, impact on all environments and human response.