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2nd Grade · 2.MD.A.1

Measuring with a ruler in 2nd grade

Measuring with a ruler means lining up one end of an object with the 0 mark and reading the number at the other end. In 2nd grade, your child learns how to use a ruler and other tools, such as a yardstick, a meter stick and a measuring tape, to find how long things are.

What the standard says

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

2.MD.A.1 Measure the length of an object by selecting and using appropriate tools such as rulers, yardsticks, meter sticks, and measuring tapes.

What it means, in plain words

Length is how long something is from one end to the other. It is measured in units. In the US, the most common units are inches and feet. Centimeters and meters are used in most other countries and in science. A school ruler is usually 12 inches long, which is 1 foot. Many rulers show inches on one edge and centimeters on the other.

Learning how to use a ruler comes down to three habits. Put the 0 mark at one end of the object. On many rulers the 0 is a little way in from the edge, so the edge itself is not the start. Keep the ruler straight along the object, then read the number at the other end and say the unit: 6 inches, not just 6.

Measuring with a ruler works for small things, like a book. Bigger things need a bigger tool. A yardstick is 3 feet long, and a meter stick is 100 centimeters long. They are the right size for a bed or a doorway. A measuring tape bends, so it works for long lengths and round things, like a kitchen floor or the distance around a pumpkin.

Your child should be able to:

  • Line up the 0 mark of a ruler with one end of an object
  • Read a length to the nearest whole unit and say the unit
  • Pick a ruler, yardstick, meter stick or measuring tape to fit the object
  • Measure something longer than the tool without gaps or overlaps

Example

A spoon starts at the 0 mark on the inch side of a ruler and ends between the 6 and the 7, much closer to the 6. How long is it to the nearest inch?

  1. One end of the spoon is at 0, so the reading starts from 0.
  2. The other end is between 6 and 7.
  3. It is closer to 6, so the spoon is about 6 inches long.

Example

A rug is longer than a yardstick. The yardstick fits along it 2 times, with 1 foot of rug left over. How long is the rug?

  1. Put the 0 end of the yardstick at one end of the rug and mark where the yardstick ends.
  2. Move the yardstick so its 0 end starts exactly at the mark. Do this again until the end of the rug.
  3. Each yardstick is 3 feet, so 3+3+1=73 + 3 + 1 = 7.
  4. The rug is 7 feet long.

Where children usually get stuck

  • Your child lines up one end of a toy car with the 1 on the ruler, reads 5 at the other end and says the car is 5 inches long. It is 4 inches.

    When counting objects, the count starts at 1. On a ruler, length is the number of inch spaces from 0. Starting at 1 and reading the last number adds a space that is not there.

    What helps. Before every measurement, ask your child to touch the 0 with a finger. Then count the spaces between the numbers out loud, one for each inch.

  • Your child measures a bed with a ruler, moving it along, but leaves gaps between moves or lets the ruler overlap.

    It is hard to see where the ruler ended once it moves. Each gap makes the answer too small, and each overlap makes it too big.

    What helps. Put a small piece of tape where the ruler ends each time. Start the next move right at the tape.

  • Your child says a length is "6 and a bit", or stops when the end of the object falls between two marks.

    Objects rarely end exactly on a mark. In 2nd grade, the answer is the nearest whole unit, the number the end is closer to.

    What helps. Measure a few things in the kitchen together, such as a fork and a cup. For each one, decide together which number the end is closer to.

Try four practice questions

Real 2nd grade questions from our question bank, easiest first. Answer them right here, check each one, and see a worked solution for any question.

  1. 1Warm-up
    Look at the ruler and the pencil. Is the ruler placed correctly?
    Yellow Pencilin123456789101112
    A
    No, the ruler is not placed correctly. The 0 mark is not at one end of the pencil.
    B
    No, the end of the ruler is not at one end of the pencil.
    C
    No, the ruler is too short for the pencil.
    D
    Yes, the ruler is placed correctly. The 0 mark is at one end of the pencil.
    Show the answer and how to solve it

    The ruler is placed correctly. The 0 mark on the ruler lines up with one end of the pencil, so the length can be read directly.

    1. 1Look at where the pencil starts on the ruler.
    2. 2The pencil's left end is at the 0 mark on the ruler.
    3. 3For the ruler to be placed correctly, the 0 mark must line up with one end of the pencil. The 0 mark is at the pencil's end, so the ruler IS placed correctly.

    Common mistake. A common mistake is thinking the ruler is correctly placed just because the object sits on top of it. To measure directly, the 0 mark — not the edge of the ruler — must line up with one end of the object.

    The idea underneath. To measure with a ruler, line up the 0 mark — not the ruler's edge — with one end of the object. The 0 mark is the true starting point for measurement.

  2. 2On level
    Sam picked a meter stick to measure a kitchen counter. Is Sam's pick a good tool for the job?
    A
    Yes, the meter stick is the right size for the kitchen counter.
    B
    No, the meter stick is too short for the kitchen counter.
    C
    No, the meter stick is too long for the kitchen counter.
    D
    No, the meter stick is for weighing, not for measuring length.
    Show the answer and how to solve it

    The answer is: Yes, the meter stick is the right size for the kitchen counter. A meter stick is about 3 feet long, which is close to the length of a kitchen counter, so it is a good fit.

    1. 1Read the scenario. Sam is using a meter stick to measure a kitchen counter.
    2. 2Think about the size of each thing. A meter stick is about 39 inches long, which is about 3 feet. A kitchen counter is usually about 3 feet from one end to the other.
    3. 3Compare the two lengths. A meter stick is about 3 feet and a kitchen counter is about 3 feet. They are close in size, so the meter stick is a good fit.
    4. 4Sam's pick is a good tool. Yes, the meter stick is the right size for the kitchen counter.

    Common mistake. A common mistake is picking 'too long' because a meter stick looks large. But a meter stick is about the same length as a kitchen counter, so it is just right.

    The idea underneath. When you choose a measuring tool, think about how the tool's length compares to the size of the object. A short tool cannot reach across a big object, and a long tool is awkward for a small object.

  3. 3On level
    Drag each item into the bin that shows the tool closest in size to the item.
    Drag each item into the group where it belongs, or tap the item, then tap the group.
    hallway
    crayon
    desk width
    Ruler
    Drag or tap items here
    Yardstick or Meter stick
    Drag or tap items here
    Measuring tape
    Drag or tap items here

    Keyboard instructions: focus an item and press Enter or Space to pick it up. Move focus to a bin or the bank and press Enter or Space to drop it. Press Escape to cancel.

    Show the answer and how to solve it

    The crayon goes in the Ruler bin. The desk width goes in the Yardstick or Meter stick bin. The hallway goes in the Measuring tape bin. Match the tool's length to the size of the thing you are measuring.

    1. 1Look at the three bins. A ruler is short. A yardstick or meter stick is about as long as a child's arm-span. A measuring tape is the longest and can also bend.
    2. 2The crayon is small, so it goes in the Ruler bin. A ruler is the right size to measure a crayon.
    3. 3The desk width is longer than a ruler but not very long. It goes in the Yardstick or Meter stick bin.
    4. 4The hallway is very long. It goes in the Measuring tape bin because a tape is long and easy to stretch out.

    Common mistake. A common mistake is putting the desk width in the Ruler bin because it is easy to spot in a classroom. A desk width is much longer than a ruler, so a yardstick or meter stick is a better match.

    The idea underneath. Measuring tools come in different lengths for a reason. Match the tool's typical length to the size of the object — short tool for short things, long tool for long things.

  4. 4Stretch
    The pinecone does not start at 0 on the ruler. How long is it in inches?
    Pineconein12345678910
    A
    2 inches
    B
    6 inches
    C
    4 inches
    D
    5 inches
    Show the answer and how to solve it

    The pinecone is 4 inches long. It spans from the 2 inch mark to the 6 inch mark, and the distance between those two marks is 4 inches.

    1. 1Look at the pinecone on the ruler. Find the inch mark where it starts and the inch mark where it ends.
    2. 2The pinecone starts at the 2 inch mark and ends at the 6 inch mark.
    3. 3To find the length, subtract the start mark from the end mark.
    4. 4The pinecone is 4 inches long.

    Common mistake. When a ruler does not start at 0, it is easy to read the end mark and call it the length. The end mark only tells you where the object stops, not how long it is. To find the length, subtract the start mark from the end mark.

    The idea underneath. The numbers on a ruler tell you positions, not lengths. To find an object's length, find the distance between where it starts and where it ends — subtract the start mark from the end mark.