A poster for the new International System of Units

Don’t worry: it probably won’t affect you.

As a species, we’re redefining the system of measurement units used by billions of people across the world.

The proposed change, expected to be adopted by the General Conference on Weights and Measures (a big meeting of government delegates to deal with this kind of thing) in November 2018, will firmly base the International System of Units on the rules of nature.

This redefinition isn’t going to change any values, but rather restructure the system of units. Rather than deriving certain constants (such as Planck’s constant and Avogadro’s constant) from empirical measurements using the units, we will redefine the units based on fixed numerical values for those constants.

For example, the kilogram will be defined by Planck’s constant, rather than the hunk of platinum-iridium metal currently sitting in a basement near Paris. (I’m serious. Watch this video from Veritasium about this.)


I made a poster to commemorate the change, using the promotional files created by the BIPM’s task group for the promotion of the SI. (I hope they don’t mind.) It gives the new definitions as they’re expected to be in effect from 2018.


I doubt the Americans are going to want to put this up on a wall, so it’s laid out on A4 paper dimensions.

It’s free for use for instructional, educational, and promotional purposes! Download a PDF version here.

Dear Professor Poliakoff

Sir Martyn Poliakoff CBE FRS, a British chemistry professor researching the applications of supercritical fluids in green chemistry. He is probably best known for his appearances in the Periodic Table of Videos by videojournalist Brady Haran at http://www.periodicvideos.com/. Photo from the Royal Society.

I write to thank you for your contributions to the promotion of science at Periodic Videos.

While I am now training to be a journalist at university, I was originally set on a career in the natural sciences. Despite my journalism background, I still find it difficult to articulate my sorrow at having given up a life of science for one of the creative arts; I have never found more accomplishment in anything than successfully grasping the intricacies of the natural sciences and coming a little bit closer to understanding the universe around me.

I believe that you have been responsible for inspiring countless young people, including myself, to gain an interest for the sciences. Your enthusiasm for and appreciation of chemistry is clearly evident whenever you appear on Periodic Videos.

Like many young people in developed societies, I believe, I grew up in an academic setting where the natural sciences were boring and repetitive — a constant drone of textbooks and theory—but my love of science was sustained because of individuals such as yourself, who demonstrate the excitement of learning and knowledge every single day.

Thank you for sharing the love of knowledge with me and everybody else. Thank you for making it cool to study science. I hope that, in addition to your scientific research, you will continue to educate and celebrate the wonders of chemistry.