The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. SI use in product design, manufacturing, marketing, and labeling is essential for United States industry's success in the global marketplace. SI measurement system familiarity and fluency must be developed along the Science, Technology, Engineering, and Mathematics (STEM) career pipeline to produce an U.S. engineering workforce with this essential 21st century skill.
In November 2018, the world’s measurement experts voted and unanimously approved a revision of the SI that establishes a measurement system entirely based on physical constants of nature. The changes took effect on World Metrology Day, May 20, 2019. Learn more about the Road to the Revised SI.
The Measurement League: Guardians of the SI are superheroes dedicated to the fight against uncertainty, imprecision, and inaccuracy and to improving the quality of our lives and the things we build, using their incredible powers of measurement to perform amazing feats of science and engineering. This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units. Videos are available on the NIST YouTube Channel.
Episode 1: Desperate Measures!
The SI Superheroes use the power of measurement to help a stranded soccer player get home.
Episode 2: Running Out of Time!
The SI Superheroes battle archvillain Major Uncertainty in a race to keep the world's satellite navigation system "on time."
Episode 3: Mass Hysteria!
The nefarious Major Uncertainty has kidnapped Monsieur Kilogram, putting the world’s measurements of mass in jeopardy.
SI Superhero Card Set (PDF) - Download a printable version of the Superhero Cards. Each card in this set lists a different superhero’s name, picture, symbol, and the measurement unit represented. A short description of the superhero’s powers are on the back of each card.
SI Measurement System Chart - SP 304A (2017) - This publication is a colorful chart explaining the 7 base units of the SI, prefix symbols, and features the Measurement League: Guardians of the SI. Submit hard copy requests to TheSI [at] nist.gov or print a copy (select “print to fit”). Original dimensions: 279 mm by 432 mm (11 in by 17 in).