1st Grade · 1.MD.A.2

Measuring length in 1st grade

Measuring length in 1st grade means finding how many small objects of the same size fit along something, end to end. Your child might measure a book with paper clips and say, "The book is 9 paper clips long." This nonstandard measurement comes before rulers and inches.

What the standard says

The official Common Core wording, quoted exactly. The plain version follows.

1.MD.A.2 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.

What it means, in plain words

A length unit is the small object you measure with, such as a paper clip, a cube or a domino. Nonstandard measurement uses everyday objects like these instead of inches or centimeters. The length is the number of units that cover the object from one end to the other.

A measurement counts only if it follows three rules. All the units are the same size. They touch end to end, with no gaps. They do not overlap. The first unit also starts exactly at one end of the object.

Measuring length this way shows your child what a ruler is: a row of same-size units already laid end to end. Rulers come in 2nd grade.

Your child should be able to:

Lay same-size units end to end along an object, starting at one end
Leave no gaps and no overlaps between units
Count the units and say the length with the unit, such as 6 cubes long
Spot a measurement that is wrong because the units are different sizes, leave gaps or overlap

Example

Cubes of the same size are laid along a toy truck with no gaps. The first cube starts at the back of the truck and the sixth cube ends at the front. How long is the truck?

The cubes are all the same size and touch end to end, so the measurement counts.
Count the cubes: 1, 2, 3, 4, 5, 6.
The truck is 6 cubes long.

Example

A shoe is measured with paper clips, but some of the clips overlap. The count is 7. Is the shoe 7 paper clips long?

Where two clips overlap, part of the shoe gets covered twice.
So 7 overlapping clips cover less than 7 clips laid end to end.
No, the shoe is shorter than 7 paper clips. Lay the clips end to end and count again.

Where children usually get stuck

Your child spreads blocks out along a book with spaces between them and says the book is 4 blocks long when it is 6.
The child thinks of measuring as reaching from one end to the other and does not see that the spaces are length too.
What helps. Measure with linking cubes, or push the blocks together like train cars so each one touches the next.
Your child mixes long and short blocks in one row and counts them all.
The child counts objects, not units of the same size, so any block seems as good as another.
What helps. Measure with one kind of object at a time, such as only paper clips, and check together that they are all the same size.
Your child measures a spoon and gives the answer as "5", with no unit.
The count feels like the whole answer. The unit seems too obvious to say, because the clips are right there.
What helps. Ask "5 what?" each time and say the full answer together: "5 paper clips long".

Try four practice questions

Real 1st grade questions from our question bank, easiest first. Answer them right here, check each one, and see a worked solution for any question.

1Warm-up
Which picture shows the scissors measured with tiles that are all the same size?
A
B
C
D
Show the answer and how to solve it
The correct picture is the one where all four tiles in the row are the same size. To measure fairly with tiles, every tile must match in size.
1. 1Look at all four pictures of the scissors. Each picture has a row of tiles below it.
2. 2Check each row carefully. In three of the pictures, one tile is bigger than the others. The bigger tile makes the row stick out past the end of the scissors.
3. 3Find the picture where every tile in the row is the same size. The row fits neatly along the scissors with no tiles sticking out.
Common mistake. A common mistake is picking a picture just because there is a row of tiles under the scissors, even when one tile is clearly bigger. A row of tiles only gives a fair measurement when all the tiles are the same size.
The idea underneath. When we measure with tiles, every tile must be the same size. If even one tile is bigger or smaller, the row of tiles does not tell us the real length of the object.
2On level
The hot dog has been measured using paper clips. How many paper clips long is the hot dog?
A
6
B
7
C
8
D
9
Show the answer and how to solve it
The hot dog is 7 paper clips long. We count each paper clip in order from one end of the hot dog to the other: 1, 2, 3, 4, 5, 6, 7.
1. 1Look at the paper clips placed end to end along the hot dog.
2. 2Count the paper clips one by one, pointing to each one: 1, 2, 3, 4, 5, 6, 7.
3. 3There are 7 paper clips. The hot dog is 7 paper clips long.
Common mistake. A common mistake is losing track and counting a paper clip twice (getting 8) or skipping a paper clip (getting 6). Pointing to each paper clip as you count helps avoid both errors.
The idea underneath. When same-size units are placed end to end along an object, the count of those units IS the length of the object measured in those units.
3On level
Liam measured this banana with tiles. It is 5 tiles long.
Look at how Liam placed the tiles. Why is this a correct way to measure the banana?
A
Because the tiles are the same size and touch end to end.
B
Because there are spaces between the tiles.
C
Because the tiles look right.
D
Because 5 is a small number.
Show the answer and how to solve it
The best reason is "Because the tiles are the same size and touch end to end." Same-size tiles placed end to end with no gaps and no overlaps are what make the count of 5 equal the length.
1. 1Look at the picture. Liam placed 5 tiles along the banana.
2. 2All the tiles are the same size, and they touch end to end with no gaps.
3. 3Count the 5 tiles. They are the same size and fit along the object with no gaps or overlaps, so the object is 5 tiles long.
4. 4The best reason is: "Because the tiles are the same size and touch end to end."
Common mistake. Spaces between tiles leave some of the length unmeasured. Here the tiles touch from one end of the object to the other, with no gaps or overlaps.
The idea underneath. Length is just how many same-size units fit end to end with no gaps or overlaps. When those two things are true, the count of units IS the length.
4Stretch
Aiyana used unit tiles to measure a paintbrush. Look at her measurement below.
Which statement is true about Aiyana's measurement?
A
The units are not all the same size. This measurement is not fair.
B
All units are the same size. This measurement is fair.
C
All units are the same size. This measurement is not fair.
D
The units are not all the same size. This measurement is fair.
Show the answer and how to solve it
The answer is 'The units are not all the same size. This measurement is not fair.' One tile in Aiyana's row is slightly bigger than the others, and a measurement is only fair when all the units are the same size.
1. 1Look at Aiyana's measurement below.
2. 2Compare the tiles. One tile is bigger than the others, so the tiles are not all the same size.
3. 3A measurement is fair only when all the units are the same size. Aiyana's tiles are different sizes, so the measurement is not fair.
4. 4The correct statement is: 'The units are not all the same size. This measurement is not fair.'
Common mistake. A common mistake is thinking the measurement is fair as long as the tiles fill the paintbrush end-to-end. But a fair measurement also needs every tile to be the same size — even a slightly bigger tile gives a different count than equal-sized tiles would.
The idea underneath. Fair measurement means equal units end to end — same-size tiles give a count that matches the true length.