by Michelle Hurst and Susan Levine, University of Chicago
Jasmine, DeShawn, and Andrea are playing with blocks and build two towers: a red tower made of three small blocks and a blue tower made of three big blocks. Jasmine says the blue tower is bigger because it’s taller, but Andrea points out that they’re both made with three blocks. DeShawn reaches for a ruler so that they can check which is bigger and know for sure. Even though DeShawn is the only one with a ruler, all the kids are measuring—just in different ways.
Young children compare and measure things all the time, and in natural and spontaneous ways. These early understandings of measurement are foundational for children’s later math learning in school. Here are some ways parents can use every day talk and playful activities to support children’s developing understanding of measurement.
Anytime we use a process to find out the size, length, or amount of something, we’re measuring. That can mean we put an object on a scale to determine its weight in pounds or use a ruler to measure an object’s length in inches. But it can also mean counting to get the total number of items in a set, or using pennies to decide a stick is 10 pennies long. Kids start comparing things very young, and they don’t need to know about formal units, like pounds and inches, to do it.
People need to measure things throughout their lives, including weight, time, length, and many other measureable dimensions. It’s likely not surprising, then, that measurement is a critical aspect of school mathematics across elementary and middle school.  Children’s early ideas about measurement, such as comparing sizes, form the basis for other important aspects of mathematical thinking and learning. 
Learning how to measure with units can be hard for young children. [3, 4] Kids need to know a lot about units and how to use them, like lining up pennies so there aren’t any gaps, or understanding that the units need to be the same size (using only pennies or only quarters rather than mixing them) to get a consistent measurement. In some cases children might create units when units aren’t obvious, like using hand lengths to measure a friend’s height.
Using a ruler can help by giving children standard units, but learning how to use a ruler can be difficult, too. For example, imagine you lined up a crayon at the 3-inch mark on a ruler, and it reached the 5-inch mark. When asked how long the crayon is, kids might say it’s 5 inches long, though it’s actually 2 inches long. Even though kids know how to compare sizes, lengths, and amounts, they might not know how these comparisons relate to formal measuring using units.
Units are important even before kids start measuring, because we use units when we count. When we count something, the thing that we’re counting is the unit. We can count trucks, fire trucks, blue trucks, truck wheels, or even all the vehicles, and the unit, the thing we are counting, changes. But this isn’t always clear to children.
In fact, children have a really hard time counting parts of objects, like the number of truck wheels, because they are so focused on the whole object, the number of trucks. Helping children make connections between units and comparisons (based on size, length, amount, etc.) can help them correctly use measurement procedures when they need to. [5, 6] Explicitly labeling the unit when counting is one way to support these connections.
You can support your young child’s early measurement skills by helping make connections between approximation, comparison, counting, and measurement. Here are some tips.
By using the language of measurement and looking for everyday ways to talk about units and measurement, you can help support your child's developing mathematical understanding.
Michelle Hurst is a post-doctoral researcher in the Department of Psychology at University of Chicago. Susan Levine is the Rebecca Anne Boylan Professor of Education and Society in the Department of Psychology at University of Chicago. Both authors are members of the DREME Network's Family Math project and Math+ project.
 Clements, D. H. (2003). Learning and Teaching Measurement (2003 Yearbook). National Council of Teachers of Mathematics. 1906 Association Drive, Reston, VA 20191-1502.
 Sophian, C. (2017). The origins of mathematical knowledge in childhood. Routledge.
 Solomon, T. L., Vasilyeva, M., Huttenlocher, J., & Levine, S. C. (2015). Minding the gap: Children’s difficulty conceptualizing spatial intervals as linear measurement units. Developmental psychology, 51(11), 1564.
 Hiebert, J. (1984). Why do some children have trouble learning measurement concepts?. The Arithmetic Teacher, 31(7), 19-24.
 Shipley, E. F., & Shepperson, B. (1990). Countable entities: Developmental changes. Cognition, 34(2), 109-136.
 Levine, S.C., Kwon, M. K., Huttenlocher, J., Ratliff, K., & Dietz, K. (2009, January). Children's understanding of ruler measurement and units of measure: A training study. In Proceedings of the Annual Meeting of the Cognitive Science Society (Vol. 31, No. 31).
 Vasilyeva, M., Casey, B. M., Dearing, E., & Ganley, C. M. (2009). Measurement skills in low-income elementary school students: Exploring the nature of gender differences. Cognition and Instruction, 27(4), 401-428.