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Estimate Lengths in Centimeters and Meters

Students develop mental benchmarks for centimeters and meters and use them to make reasonable estimates of object lengths in metric units. Students compare their estimates to actual measurements.

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Estimate Lengths in Centimeters and Meters

Grade 2 · Measuring Length · question 1 of 3

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12 rungs. A star at the top.

Which unit is best to estimate the length of a pencil?

How it is taught

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A centimeter is about a fingernail.

A meter is about as tall as a first grader.

Read it: Estimate with a unit you know

How tall is a door? 1 meter is about 1 big step. A door is about 2 of those: about 2 m.

  1. Think of a unit you know: 1 meter, 1 centimeter, 1 inch or 1 foot.
  2. Picture it laid along the thing, again and again.
  3. Say about how many: a door is about 2 m.

You cannot always use a ruler, so you think of a unit you know.

1 meter is about a big step, 1 centimeter a fingernail's width, 1 inch a thumb's width, and 1 foot a long ruler.

Big things are measured in meters, feet or yards. Small things are measured in centimeters or inches.

An estimate is a careful guess with a unit you know.

Saying a door is 2 cm tall, because the number 2 sounds right.

2 cm is 2 fingernails. A door is about 2 big steps: 2 m.

1 big step is about 1 meter. A rug is about 3 big steps long. About how many meters long is the rug? — 3. 3 big steps is about 3 meters, so the rug is about 3 m.

How long is this pencil?

Today we'll estimate lengths. How long do you think this pencil is?

Your fingernail is about one centimeter wide. Centimeters are small.

A big step is about one meter — that's one hundred centimeters.

A pencil is small, so centimeters is the right unit to use.

I'll estimate about eighteen centimeters — a little shorter than two hands.

Now let's check with a centimeter ruler.

Grade 2 · Picking the right unit and making smart estimates

Line up the end of the pencil with zero on the ruler.

The pencil reaches eighteen — eighteen centimeters!

Our estimate matched! Use centimeters for small things, meters for big things.

Now you try. Read how long this object is on the ruler. What length do you read?

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics
Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal
1 star — one skill mastered, every rung of its ladder climbed
Climbing now
Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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