Metric and Imperial Unit Conversions Lesson

Lesson Overview

• Understanding Measurement Systems
• Metric Unit Prefixes
• Converting Length in the Metric System
• Converting Weight in the Metric System
• Converting Volume in the Metric System
• Converting Between Metric and Imperial Units
• Converting Weight Between Kilograms and Pounds
• Converting Gallons to Liters and Vice Versa
• Area Unit Conversion (Square Units)
• Converting Time Units
• Speed Unit Conversion
• Scientific Notation in Conversions

Unit conversion means changing a number or amount from one unit of measurement to another. This helps us work with different units used to measure length, weight, volume, area, time, and even speed.

Unit conversion is important in math, science, and daily life. If you're solving math problems, reading a recipe, or measuring distance, knowing how to convert between units helps you work accurately and confidently.

This lesson will teach you how to use conversion factors to switch between different units. We'll learn how to convert units within the metric system, how to compare metric and imperial units, and how to convert units for time, area, and speed.

Understanding Measurement Systems

There are two main systems of measurement:

➤ Metric System

• Used in most parts of the world
  
• Based on multiples of 10
  
• Easier to convert between units
  
• Common metric units: meter, kilogram, liter
  

➤ Imperial System

• Mostly used in the United States
  
• Does not follow powers of 10
  
• Common imperial units: inch, foot, pound, gallon
  

When converting units, we either:

• Multiply (to get a larger number of smaller units)
  
• Divide (to get a smaller number of larger units)
  

Metric Unit Prefixes

The metric system uses prefixes to show how big or small a unit is compared to the base unit.

Base units include:

• Meter (m) for length
  
• Liter (L) for volume
  
• Gram (g) for weight
  

Knowing these prefixes helps you convert within the metric system by simply moving the decimal point.

Take This Quiz:

Unit Conversion Quiz Questions and Answers

Converting Length in the Metric System

➤ Common length units:

• Millimeter (mm)
  
• Centimeter (cm)
  
• Meter (m)
  
• Kilometer (km)
  

1 meter = 100 centimeters
1 kilometer = 1,000 meters

Example 1: Convert 2.5 kilometers to meters

2.5 km × 1000 = 2,500 meters

Example 2: Convert 45 centimeters to meters

45 ÷ 100 = 0.45 meters

Example 3: Convert 14 millimeters to meters

14 ÷ 1000 = 0.014 meters

Use multiplication when converting to smaller units, and division when converting to larger units.

Converting Weight in the Metric System

➤ Common weight units:

• Gram (g)
  
• Kilogram (kg)
  

1 kilogram = 1,000 grams

Example 1: Convert 3 kilograms to grams

3 × 1,000 = 3,000 grams

Example 2: Convert 2,500 grams to kilograms

2,500 ÷ 1,000 = 2.5 kilograms

Always pay attention to whether you're increasing or decreasing the size of the unit.

Converting Volume in the Metric System

➤ Common volume units:

• Milliliter (mL)
  
• Liter (L)
  

1 liter = 1,000 milliliters

Example 1: Convert 0.75 L to milliliters

0.75 × 1,000 = 750 mL

Example 2: Convert 57 mL to liters

57 ÷ 1,000 = 0.057 L

These conversions are especially useful in science and cooking.

Take This Quiz:

Test Your Knowledge of Metric System With Metric Conversions Quiz!

Converting Between Metric and Imperial Units

When switching between metric and imperial systems, you must use conversion factors.

Example: Convert 10 meters to inches

10 × 39.37 = 393.7 inches

Example: Convert 355 millimeters to inches

355 ÷ 25.4 = 13.98 inches

These conversions require multiplying or dividing by the correct factor.

Converting Weight Between Kilograms and Pounds

Example: Convert 5 kg to pounds

5 × 2.2046 = 11.02 pounds

Example: Convert 10 pounds to kilograms

10 ÷ 2.2046 = 4.54 kilograms

Remember to round answers to two decimal places when needed.

Converting Gallons to Liters and Vice Versa

Example: Convert 3.5 gallons to liters

3.5 × 3.7854 = 13.25 L

Example: Convert 15 liters to gallons

15 × 0.2642 = 3.96 gallons

You can use these conversions in tasks like measuring fuel, water, or other liquids.

Area Unit Conversion (Square Units)

When converting area units like square meters and square feet, you must square the conversion factor.

Example: Convert 250 ft² to m²

250 × 0.092903 = 23.23 m²

Area conversions are used in flooring, gardening, and real estate.

Take This Quiz:

Unit 4 Conversions Quiz

Converting Time Units

Time conversions are based on simple, consistent numbers.

Example: Convert 34.5 years to hours

34.5 × 365 = 12,592.5 days
12,592.5 × 24 = 302,220 hours

Always convert one step at a time: years → days → hours.

Speed Unit Conversion

To convert miles per hour (mph) to meters per second (m/s):

1 mph = 0.44704 m/s

Example: Convert 45 mph to m/s

45 × 0.44704 = 20.12 m/s

Speed conversions are useful in physics, sports, and transportation.

Scientific Notation in Conversions

Sometimes, small or large values are written using scientific notation (like 1.23 × 10⁻⁶).

Example: Convert 1.23 × 10⁻⁶ km to cm

1 km = 100,000 cm
1.23 × 10⁻⁶ × 100,000 = 0.123 cm

Use the powers of 10 carefully in scientific conversions.