Researchers have said that they are close to redefining the kilogram so it is based on a physical constant, rather than on a piece of metal kept in Paris.
Scientists held a discussion on the research, which seeks to define a kilogram in terms of the fundamental Planck constant, rather than a manufactured object, on Monday at the UK's national academy of science, the Royal Society.
"In the near future the kilogram shall be redefined, based on a fixed value of the Planck constant," Michael Stock of the the Bureau International des Poids et Mesures (BIPM) said in a statement. "Our experiments are moving forward, however, it is too early to implement the new definition of the kilogram just yet."
The researchers said that the kilogram on which all others are based, which is made of platinum-iridium and housed at the BIPM in France, has lost 50 micrograms over the past 100 years, and they do not know why.
50 micrograms is equivalent to a grain of sand 0.4mm in diameter.