text: when we say our weight is 70 kilograms, is it that our mass is 70 kilograms or that our weight is 70 newtons?   the terminology is at fault due to convention here.  when we say 'weight' in terms of how fat we are, we actually are measuring mass when se state it in kg or pounds and stone.  sticking to the si system of units (kg), we use newtons 2nd law of motion:  f=m.a  here: f is the force in newtons       m is the 'mass' of the subject       a is the acceleration field the mass experiences.  the accelerating field here on earth is typically 9.81m/s/s.  thats the gravitational acceleration due to the cumlative effect of the earths mass.  however, many people round this figure reasonably up to 10 m/s/s.  this in turn means that a mass of 1 kg would result in a force of 10 newtons here on earth (using the 10 m/s/s) approx).  therefore your 'mass' of 70 kg would have a force of 700 newtons here on earth.  typically we take the earths acceleration field due to gravity for granted and thus refer to all mass measurements on earth as 'weight'.  therefore, to summarize, on earth, your mass is 70 kg, its weight is 700n and its effective force due to the earths gravitational field is also 700 n.  get confusing.. its got good reasoning in physics to be refered to as mass rather than the inaccurate weight.  hope that helped.