Well, not really – what is changing is the reference weight. In May 2019, a Kilogram will no longer be defined by a chunk of metal stored in a vault in Paris.

It will be defined as a function of electromagnetic force. If you are a Physics geek, you will really enjoy this post from The Verge. If you are not, well, skim over it anyway – it’s fascinating.

https://www.theverge.com/2018/11/13/18087002/kilogram-new-definition-kg-metric-unit-ipk-measurement