July 2015

The Metric System

A Position of the National Council of Teachers of Mathematics

Question

What should schools teach about the metric system?

NCTM Position

Students need to develop an understanding of metric units and their relationships, as well as 

fluency in applying the metric system to real-world situations. Because some non-metric units of 

measure are common in particular contexts, students need to develop familiarity with multiple 

systems of measure, including metric and customary systems and their relationships.

The International System of Units (SI) is the internationally recognized standard metric

system. Almost all countries have adapted SI, although some have retained elements of

their non-metric units of measure for use in everyday life. Understanding relationships 

between SI and customary systems of measure is important to students, who must be able 

to communicate in a technology-rich world and work in a global economy. In particular, SI

is the predominant measurement system in science and prevalent in commerce (Thompson & 

Taylor, 2008). To participate in integrated science, technology, engineering, and 

mathematics (STEM) fields, students need to be fluent in applying the metric system.

NCTM Standards, the Common Core State Standards for Mathematics, and the Next 

Generation Science Standards all describe the need to organize curriculum to ensure that

students become proficient in measurement. Students should gradually develop fundamental 

ideas of measurement that lead to understanding SI and customary systems as two examples 

of systems of measure. Students first need to develop a concept of the attribute to be measured

(e.g., length, mass, volume, time, temperature) by comparing and ordering objects solely on

the basis of that attribute. Then they should devise and apply nonstandard units to compare

and order objects indirectly on the basis of the attribute. Finally, they should be introduced to

standard units of measure (both SI units and non-metric units of measure customarily used in 

the United States) and systems of measure. 

Within the study of a system of measure, learning goals for students should include knowledge 

of and ability to use referents, or benchmarks, in estimation. Students should select appropriate

units for a given task and make reasonably accurate measurements by using standard tools. 

They should reason proportionally to develop relationships between units in different systems 

and convert flexibly and fluently among commonly used units within a measurement system.

Students should experience the usefulness of systems of measure for meaningful 

communication and develop an appreciation for their value. Standard systems of measure 

allow reliability—repeated measures of an object’s attribute within one system yield 

consistent results. Two or more people who use the same system of units can share a common

understanding of measures of an object’s attributes, regardless of whether the people are in 

the same location as the object or as one another. These features allow for shared 

discoveries and meaningful communication in STEM fields.
Metric System—NCTM position statement

July 2015

References

National Council of Teachers of Mathematics. (2000). Principles and standards for school 

mathematics. Reston, VA: Author. 

National Governors Association Center for Best Practices & Council of Chief State School Officers. 

(2010). Common core state standards for mathematics. Common core state standards (college- and 

career-readiness standards and K–12 standards in English language arts and math). Washington, 

DC: Author. http://www.corestandards.org

National Science Teachers Association. (2012). Next Generation Science Standards. Washington, 

DC: Author. http://www.nextgenscience.org/

Thompson, A., & Taylor, B. N. (2008). Guide for the use of the International System of Units (SI). 

Washington, DC: National Institute of Standards and Technology. Retrieved from 

http://physics.nist.gov/cuu/pdf/sp811.pdf

Resources

Albrecht, M. R., Burke, M. J., Ellis, W., Jr., Kennedy, D., & Maletsky, E. M. (2004). Navigating 

through Measurement in Grades 9–12. Reston, VA: National Council of Teachers of 

Mathematics. 

Anderson, N. C., & Cuevas, G. J. (2005). Navigating through measurement in grades 3–5. 

Reston, VA: National Council of Teachers of Mathematics.

Bright, G. W., Jordan, P. L., Malloy, C., & Watanabe, T. (2005). Navigating through 

measurement in grades 6–8. Reston, VA: National Council of Teachers of Mathematics.

Clements, D. H. (Ed.). (2003). Learning and teaching measurement, 2003 Yearbook of the 

National Council of Teachers of Mathematics (NCTM). Reston, VA: NCTM.

Dacey, L., Cavanagh, M., Findell, C. R., Greenes, C. E., Sheffield, L. J., & Small, M. (2003).

Navigating through measurement in prekindergarten–grade 2. Reston, VA: National Council 

of Teachers of Mathematics.

Dougherty, B. J., Flores, A., Louis, E., & Sophian, C. (2010). Developing essential 

understanding of number and numeration for teaching mathematics in prekindergarten–

grade 2. Essential Understanding Series. Reston, VA: National Council of Teachers of 

Mathematics. 

Goldenberg, E. P., & Clements, D. H. (2015). Developing essential understanding of geometry 

for teaching mathematics in prekindergarten–grade 2. Essential Understanding Series. 

Reston, Va.: National Council of Teachers of Mathematics.

National Council of Teachers of Mathematics. (2012). Real world math: Articles, lesson plans, 

and activities for the middle grades. Reston, VA: Author. 

http://www.nctm.org/store/Products/Real-World-Math--Articles,-Lesson-Plans,-andActivities-for-the-Middle-Grades/

National Council of Teachers of Mathematics. (October, 2006). Teaching and learning 

measurement (focus issue). Teaching Children Mathematics.

National Council of Teachers of Mathematics. (February, 2013). Mathematics in a STEM 

context (focus issue). Mathematics Teaching in the Middle School.