WE first derive for jet aeroplanes the formulae for the least thrust sufficient for a specified angle of climb. In the mathematical derivation of formulae we make use of the method represented by H. Freeman in J. of Ae. Sci. No. 3/1947, ‘Simple Analytic Equations for the Velocity of an Aeroplane in Unaccelerated Level, Climbing and Diving Flight’. We then see that through a simple deformation the equations can be brought into such a form as to make it possible to represent the steepest climbing angle, the corresponding flight velocity and the rate of climb obtainable at a specified thrust by means of a combined, very simple, dimensionless vector diagram.