Inches and Feet
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In the United States, we measure length using inches and feet. These are called customary units. Let us learn how to measure with them!
What Is an Inch?
An inch is a small unit of length. It is about the width of a quarter or the length from the tip of your thumb to the first knuckle.
We use the symbol in for inches. Example: 5 in
What Is a Foot?
A foot is a bigger unit of length. It is about the length of a ruler or a big adult shoe.
We use the symbol ft for feet. Example: 3 ft
The Big Rule: 12 Inches = 1 Foot
This is very important to remember:
12 inches = 1 foot
A standard ruler is 12 inches long, which is the same as 1 foot!
When to Use Each Unit
- Use inches for small things: pencils, books, your hand
- Use feet for bigger things: doors, desks, how tall you are
Using a Ruler
To measure with a ruler:
- Line up the object with the 0 mark on the ruler
- Look at where the object ends
- Read the number - that is how many inches!
Worked Examples
Example 1: Measuring a Pencil
Problem: A pencil is 7 inches long. Is that more or less than 1 foot?
Step 1: Remember: 1 foot = 12 inches
Step 2: Compare: 7 inches and 12 inches
Step 3: 7 is less than 12
Answer: 7 inches is less than 1 foot
Example 2: Converting Feet to Inches
Problem: How many inches are in 2 feet?
Step 1: 1 foot = 12 inches
Step 2: 2 feet = 12 + 12 = 24 inches
Answer: 2 feet = 24 inches
Example 3: Choosing the Right Unit
Problem: Would you measure a door in inches or feet?
Step 1: Think about the size of a door - it is tall!
Step 2: Feet are better for big things
Answer: Measure a door in feet (a door is about 7 feet tall)
Example 4: Adding Lengths
Problem: One ribbon is 5 inches. Another is 8 inches. How long are they together?
Step 1: Add the inches: 5 + 8 = 13 inches
Step 2: 13 inches is more than 12 inches (1 foot)
Answer: 13 inches, or 1 foot and 1 inch
Example 5: Real World Measurement
Problem: A child is 4 feet tall. How many inches is that?
Step 1: 1 foot = 12 inches
Step 2: 4 feet = 12 + 12 + 12 + 12 = 48 inches
Answer: 4 feet = 48 inches
Practice Problems
Try these problems on your own. Click "Show Answer" to check your work!
Problem 1: How many inches are in 1 foot?
Show Answer
12 inches
Problem 2: Is 15 inches more or less than 1 foot?
Show Answer
More (15 is greater than 12)
Problem 3: How many inches are in 3 feet?
Show Answer
36 inches (12 + 12 + 12 = 36)
Problem 4: Would you measure a crayon in inches or feet?
Show Answer
Inches - A crayon is small, so inches work better.
Problem 5: A book is 9 inches tall. How much more to make 1 foot?
Show Answer
3 inches (12 - 9 = 3)
Problem 6: Which is longer: 2 feet or 20 inches?
Show Answer
2 feet (2 feet = 24 inches, which is more than 20 inches)
Problem 7: A snake is 5 feet long. How many inches is that?
Show Answer
60 inches (5 x 12 = 60)
Problem 8: Would you measure a classroom in inches or feet?
Show Answer
Feet - A classroom is big, so feet work better.
Problem 9: A string is 24 inches. How many feet is that?
Show Answer
2 feet (24 / 12 = 2)
Problem 10: Which is longer: 1 foot or 10 inches?
Show Answer
1 foot (1 foot = 12 inches, which is more than 10)
Check Your Understanding
Question 1: What is the relationship between inches and feet?
Show Answer
12 inches = 1 foot. Inches are smaller units, and feet are bigger units.
Question 2: When should you use inches instead of feet?
Show Answer
Use inches for small objects like pencils, books, and hands. Use feet for bigger things like rooms, doors, and how tall people are.
Question 3: How many inches are in 4 feet?
Show Answer
48 inches (4 x 12 = 48)
Question 4: A ruler is usually how long?
Show Answer
A standard ruler is 12 inches long, which equals 1 foot.
Next Steps
- Practice: Measure objects around your home with a ruler
- Estimate: Guess how long something is, then measure to check
- Next Lesson: Learn about centimeters and meters!
- Real Life: Notice when adults talk about inches and feet