Measurement

Measurement means finding out how long, tall, or heavy something is by using a tool or by counting units.

Reading is good — doing is better. Practice Measurement as an interactive lesson.

Definition

Measurement is the way we find the size of something. In 1st grade, we mostly measure how long or tall things are. We can use a ruler, a measuring tape, or even small objects like paper clips or cubes lined up in a row to measure.

Remember the rule

Line up one end with zero, then read the number at the other end — that is your measurement!

Key words

Length: How long something is from one end to the other.
Height: How tall something is from bottom to top.
Unit: The thing you use to measure, like an inch, a centimeter, or a paper clip.
Ruler: A flat tool with numbers on it used to measure length.
Inch: A small unit of length used in the United States. Your thumb is about 1 inch wide.
Centimeter: A very small unit of length. About the width of your pinky fingernail.
Estimate: A smart guess about how long something is before you measure it.
Compare: To look at two things and decide which one is longer, shorter, or the same length.

Worked examples

A crayon is laid next to a ruler. One end is at 0 and the other end is at 5. How long is the crayon?

→ The crayon is 5 inches long. · Always start measuring from 0, not from the number 1.

You line up 4 paper clips end to end along a pencil and the pencil is exactly as long as all 4 paper clips. How long is the pencil in paper clips?

→ The pencil is 4 paper clips long. · The paper clip is acting as the unit of measurement here.

A book is 8 centimeters tall and a box is 12 centimeters tall. Which one is taller?

→ The box is taller because 12 is more than 8.

A worm is about 3 inches long. A stick is about 7 inches long. How much longer is the stick than the worm?

→ The stick is 4 inches longer because 7 minus 3 equals 4.

You estimate that a table is about 10 cubes long. You then measure and count 13 cubes. Was your estimate close?

→ Yes, 10 is pretty close to 13, so that was a good estimate. · An estimate does not have to be perfect, just a reasonable guess.

Common mistakes

Starting to measure from the number 1 instead of from 0 on the ruler, which makes the answer too small by 1.
Leaving gaps between the units when using paper clips or cubes, which makes the object seem shorter than it really is.
Overlapping the paper clips or cubes so they stack on each other, which makes the object seem longer than it really is.
Mixing up length and height — length goes side to side, height goes up and down, but both are measured the same way.
Forgetting to name the unit in the answer, for example saying '5' instead of '5 inches' or '5 cubes'.

FAQs

Why do we start measuring at 0 and not at 1?

The ruler counts the spaces between the marks, not the marks themselves. If you start at 1, you are skipping the first space, so your answer will be one unit too small.

Can I use anything as a unit to measure?

Yes! You can use paper clips, cubes, your hand, or any object as long as you use the same size object every time and do not leave gaps or overlaps.

What is the difference between inches and centimeters?

They are just two different units for measuring length. An inch is bigger than a centimeter. There are about 2 and a half centimeters in one inch.

How do I measure something that is longer than my ruler?

You can mark where the ruler ends, then move the ruler and keep counting. You add up both parts to get the total length.

Why does my answer look different from my friend's answer when we measure the same thing?

You might have used a different unit. If you used big paper clips and your friend used small paper clips, you will get different numbers. Always check that you used the same size unit.

What does it mean to compare lengths?

Comparing means looking at two objects side by side and deciding which is longer, which is shorter, or if they are the same length. You can line them up at the same starting point to make it easy to see.

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