1st Grade · Measurement & Data
1.MD.A.2: Express the length of an object as a whole number of length units
1.MD.A.2 is a 1st grade Common Core math standard in Measurement & Data. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Express the length of an object as a whole number of length units, by laying multiple copies of a shorter object (the length unit) end to end; understand that the length measurement of an object is the number of same-size length units that span it with no gaps or overlaps. Limit to contexts where the object being measured is spanned by a whole number of length units with no gaps or overlaps.
In plain words
Express the length of an object as a whole number of length units.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
If a pen is 3 paper clips long, how many paper clips long are two pens?
- 3
- 5
- 6
Where students can get stuck
- Leaving gaps between the paper clips or blocks, so the object seems longer than it really is.
- Mixing units of different sizes, like big and small paper clips, and still counting each one as one unit.
- Starting away from the edge of the object, or letting the last unit hang far past the end, and counting it anyway.
Effective teaching strategies
- Lay paper clips end to end along a pencil with no gaps and no overlaps, starting at the pencil's left edge, and have students count them.
- Offer two sizes of paper clip and ask what goes wrong when one pencil is measured with some of each, then have students measure again with one size.
- Have students say each length as a number with its unit, such as “6 cubes long,” and check that the first cube starts at one edge and the last ends at the other.
Units that teach this standard
Find where 1.MD.A.2 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Everyday Mathematics
Go Math!
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Measuring length by lining up same-size objects for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice measurement and data at home
In Bobby's Math Club, students practice at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free for every family.
See how it works for teachers
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.