The Porpoise-class submarines were  long overall and  between perpendiculars, with a beam of  and a draught of . Displacement was  standard and  full load surfaced and  submerged.
The Porpoise-class submarines were  long overall and  wide between perpendiculars, with a beam of  and a draught of . Displacement was  standard and  full load surfaced and  submerged, which is similar to other types of vessels.