Early Math · Grade 2
Measuring in Inches, Feet, Centimeters and Meters
Quick answer
Length is measured in standard units: inches, feet and yards, or centimeters and meters. A ruler counts units from its 0 mark, so the end of the object must sit at 0. Measuring the same thing in a bigger unit gives a smaller number, because fewer of the bigger units fit: a pencil is about 6 inches or about 15 centimeters. To find how much longer one thing is than another, measure both in the same unit and subtract.
What you'll learn
- Choose a tool and measure a length with it, starting at 0
- Measure one length in two units and explain why the numbers differ
- Estimate lengths in inches, feet, centimeters and meters
- Find how much longer one object is than another
Units and tools
Standard units are the same size everywhere, so everyone’s measurements match.
| Unit | About as long as |
|---|---|
| inch | the width of a quarter |
| foot ( inches) | a sheet of paper, the long way |
| yard ( feet) | a big step |
| centimeter | the width of a fingernail |
| meter ( centimeters) | a little more than a yard |
Pick a tool that fits the job. A ruler is good for a pencil. A yardstick or meter stick is good for a table. A measuring tape bends, so it can go around a head or stretch across a room.
Measure with a ruler
Put one end of the pencil at the 0 mark. Then read the number at the other end.
The pencil ends at . It is inches long.
Why you start at 0
Each number on a ruler counts how many units there are from 0. The mark is units from .
If the pencil starts at the mark, the first unit is skipped. The end lands on , but the pencil is still long.
A ruler reading is only the length when the object starts at . Starting at adds one unit that is not there. (If you do start at , subtract: .)
Big units, small numbers
Measure one rope two ways: with small cubes, then with cubes twice as long.
It takes small cubes but only big ones. The rope did not change. The unit did.
The bigger the unit, the fewer of them fit. So a pencil is about inches but about centimeters, because a centimeter is much smaller than an inch.
Estimate
To estimate, picture a unit you know and ask how many would fit.
A book is about foot long. A door is about meters tall. A paper clip is about centimeters long.
Worked examples
Common mistakes
Practice problems
-
How long is the key?
A key and a ruler Answer
inches
Full solution
The key starts at and ends at the mark.
-
Which tool would you use to measure the length of a room: a ruler or a measuring tape?
Answer
A measuring tape
Full solution
A room is much longer than a ruler. A measuring tape stretches all the way across.
-
How many inches are in a foot?
Answer
Full solution
A foot is inches. Most rulers are one foot long.
-
A spoon is inches long. A fork is inches long. How much longer is the fork?
Answer
inches
Full solution
Both are in inches, so subtract: .
-
Would you measure a phone in centimeters or in meters?
Answer
Centimeters
Full solution
A phone is much shorter than a meter. Centimeters are small enough to count along it.
-
A table is big steps long. Would it be more or fewer steps if you took small steps?
Answer
More
Full solution
Smaller units fit more times along the same length. So small steps give a bigger number.
-
How long is this marker? Watch where it starts.
A marker and a ruler Answer
inches
Full solution
It starts at , not , and ends at . So it is inches long.
-
Estimate: is a new crayon about centimeters or about meters long?
Answer
About centimeters
Full solution
A meter is longer than a yard. A crayon fits in your hand, so centimeters make sense.
-
A rope is feet long. How many inches is that?
Answer
inches
Full solution
Each foot is inches: .
-
Ben puts a pencil at the edge of a ruler, not at , and reads . Is the pencil exactly inches long?
Hint
Where do the ruler’s units start?
Answer
Not quite. It is a little longer than inches.
Full solution
The pencil also covers the space between the edge and . The ruler’s numbers do not count that bit.
So the pencil is inches plus a little more. Line it up with to measure it.
Frequently asked questions
Where do I start measuring on a ruler?
At the 0 mark. Line up one end of the object with 0, then read the number at the other end.
How long is an inch? A centimeter?
An inch is about the width of a quarter. A centimeter is about the width of a fingernail, or one small base-ten cube.
How many inches are in a foot?
12. A ruler is often one foot long. Three feet make a yard, and 100 centimeters make a meter.
Why is a length a smaller number in inches than in centimeters?
An inch is longer than a centimeter, so fewer inches fit along the same thing. Bigger units, smaller number.
How do I find how much longer one thing is?
Measure both in the same unit, then subtract the shorter length from the longer one.
Standards alignment
This lesson covers the following Common Core State Standards for Mathematics.
- CCSS.MATH.CONTENT.2.MD.A.1Measurement and DataMeasure the length of an object by selecting and using appropriate tools such as rulers, yardsticks, meter sticks, and measuring tapes.
- CCSS.MATH.CONTENT.2.MD.A.2Measurement and DataMeasure the length of an object twice, using length units of different lengths for the two measurements; describe how the two measurements relate to the size of the unit chosen.
- CCSS.MATH.CONTENT.2.MD.A.3Measurement and DataEstimate lengths using units of inches, feet, centimeters, and meters.
- CCSS.MATH.CONTENT.2.MD.A.4Measurement and DataMeasure to determine how much longer one object is than another, expressing the length difference in terms of a standard length unit.