There can be no equivalence.
5'1" is a measure of length or distance in 1-dimensional space while a weight is a measure of force. The two measure different things and, according to basic principles of dimensional analysis, any attempt at conversion from one to the other is fundamentally flawed.
It cannot be determined whether a 51-year old man or woman is overweight at 51 kilograms of weight. This is because the ideal weight of a person is based on how heavy he or she is.
51 kilograms is 112.44 pounds.
51 kilos
51 kilos
Generally at the age of 51, female will gain some unwanted weight. 56 to 60kg (125-132 pounds) of weight is recommended to 51 years female with 5’5 height.
51-57kg
my weight is 146lb and my ht is 4'11
51-57kg
There is no particular weight for a 51-year-old. This is because weight is related to height and body composition rather than age.
51 g
112 lbs (51 kgs)
he only weighs 51 kgs