2nd Grade · Measurement & Data
2.MD.A.3: Estimate lengths using units of inches, feet, centimeters, and meters
2.MD.A.3 is a 2nd 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
Estimate lengths using units of inches, feet, centimeters, and meters.
In plain words
Estimate lengths using units of inches, feet, centimeters, and meters.
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
About how long is a new crayon?
- 10 meters
- 10 feet
- 10 centimeters
Where students can get stuck
- Guessing wildly, such as a 50-inch pencil or a 3-centimeter classroom, because the units have no meaning yet.
- Mixing up which unit is bigger, thinking a centimeter is longer than an inch or a foot longer than a meter.
- Treating an estimate as wrong unless it matches the measurement exactly, then not wanting to guess at all.
Effective teaching strategies
- Have students find personal benchmarks, such as a thumb’s width for about 1 inch and a pinky fingernail’s width for about 1 centimeter, and use them to estimate lengths.
- Ask students to estimate first, then measure, and celebrate an estimate that is close rather than only one that is exact.
- Offer three choices such as 7 inches, 7 feet, and 7 meters for the length of a pencil, and have students pick one and argue why the others are not reasonable.
Units that teach this standard
Find where 2.MD.A.3 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
Eureka Math²
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Estimating lengths in inches, feet, and meters 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.