Unit Conversion | CSE Reviewer

What Is Unit Conversion?

Unit conversion is changing a measurement from one unit to another. For example, changing 2 meters to centimeters, or 3 pounds to kilograms.

To convert, you need to know the conversion factor (how many of one unit equals another).

Tip: Think of conversion as multiplying or dividing by a number you already know.

Example: Change 3 meters to centimeters.

Step 1: Know the conversion → 1 meter = 100 centimeters
Step 2: Multiply → \(3 × 100 = 300\)

Answer: 300 centimeters

Meaning: Unit conversion changes a measurement to a different unit using a known conversion factor.

Key Conversion Factors

Here are the most common conversion factors you need to remember. Learn these well!

Length (Metric):

From	To	Multiply By
1 kilometer (km)	meters (m)	1,000
1 meter (m)	centimeters (cm)	100
1 centimeter (cm)	millimeters (mm)	10

Length (Imperial):

From	To	Multiply By
1 foot	inches	12
1 yard	feet	3
1 mile	feet	5,280

Weight:

From	To	Multiply By
1 kilogram (kg)	grams (g)	1,000
1 pound (lb)	grams (g)	≈ 454
1 pound (lb)	kilograms (kg)	≈ 0.454

Volume:

From	To	Multiply By
1 liter (L)	milliliters (mL)	1,000
1 cup	milliliters (mL)	≈ 237
1 gallon	liters (L)	≈ 3.785

These are the most common conversion factors. Memorize them to convert quickly.

Converting Larger to Smaller Units

When you convert from a larger unit to a smaller unit, you multiply. This is because you need more of the smaller units to make the same amount.

Step-by-step to convert 2.5 km to meters:

• Step 1: Identify larger and smaller units → km is larger, m is smaller
• Step 2: Know the conversion factor → 1 km = 1,000 m
• Step 3: Multiply → \(2.5 × 1,000 = 2,500\)
• Step 4: Write answer with new unit → 2,500 m

Shortcut: Larger to smaller → Multiply. Think: "I need more small units."

Example 1: Convert 3 meters to centimeters.

Step 1: m is larger, cm is smaller
Step 2: 1 m = 100 cm
Step 3: Multiply → \(3 × 100 = 300\)

Answer: 300 cm

Example 2: Convert 1.5 kg to grams.

Step 1: kg is larger, g is smaller
Step 2: 1 kg = 1,000 g
Step 3: Multiply → \(1.5 × 1,000 = 1,500\)

Answer: 1,500 g

Meaning: To convert larger to smaller units, multiply by the conversion factor.

Converting Smaller to Larger Units

When you convert from a smaller unit to a larger unit, you divide. This is because you need fewer of the larger units to make the same amount.

Step-by-step to convert 2,500 meters to kilometers:

• Step 1: Identify smaller and larger units → m is smaller, km is larger
• Step 2: Know the conversion factor → 1 km = 1,000 m
• Step 3: Divide → \(2,500 ÷ 1,000 = 2.5\)
• Step 4: Write answer with new unit → 2.5 km

Shortcut: Smaller to larger → Divide. Think: "I need fewer big units."

Example 1: Convert 500 cm to meters.

Step 1: cm is smaller, m is larger
Step 2: 1 m = 100 cm
Step 3: Divide → \(500 ÷ 100 = 5\)

Answer: 5 m

Example 2: Convert 3,000 g to kg.

Step 1: g is smaller, kg is larger
Step 2: 1 kg = 1,000 g
Step 3: Divide → \(3,000 ÷ 1,000 = 3\)

Answer: 3 kg

Meaning: To convert smaller to larger units, divide by the conversion factor.

Converting Between Metric and Imperial

When converting between metric and imperial units, use the known conversion factor. You still multiply or divide the same way.

Common Conversion Factors:
- 1 inch = 2.54 cm
- 1 foot = 30.48 cm
- 1 mile = 1.609 km
- 1 pound = 0.454 kg

Example 1: Convert 10 inches to centimeters.

Step 1: inches to cm → larger to smaller? No, just use factor
Step 2: 1 inch = 2.54 cm
Step 3: Multiply → \(10 × 2.54 = 25.4\)

Answer: 25.4 cm

Example 2: Convert 5 km to miles.

Step 1: km to miles → smaller to larger? Yes
Step 2: 1 mile = 1.609 km
Step 3: Divide → \(5 ÷ 1.609 ≈ 3.11\)

Answer: ≈ 3.11 miles

Overall meaning: Use the conversion factor and multiply or divide like normal.

Tips and Shortcuts for Unit Conversion

Unit conversion can be fast if you use shortcuts. Here are the best tips.

Tips:

• Larger to smaller → Multiply
• Smaller to larger → Divide
• Metric: 1 km = 1,000 m, 1 m = 100 cm, 1 kg = 1,000 g, 1 L = 1,000 mL
• Imperial: 1 foot = 12 inches, 1 yard = 3 feet
• 1 inch = 2.54 cm (exact)
• 1 pound ≈ 0.454 kg (or 1 kg ≈ 2.2 pounds)
• For quick mental math: 1 kg ≈ 2.2 lb, so to convert kg to lb, multiply by 2.2

Example Shortcut: When shopping, 1 kg ≈ 2.2 pounds. So if you see 5 kg, think "about 11 pounds" (5 × 2.2 = 11).

Example: 3 kg of rice → \(3 × 2.2 = 6.6\) pounds

More Practice Examples

Example 1: Convert 2.5 hours to minutes.
Step 1: 1 hour = 60 minutes
Step 2: Multiply → \(2.5 × 60 = 150\)
Answer: 150 minutes

Example 2: Convert 180 seconds to minutes.
Step 1: 1 minute = 60 seconds
Step 2: Divide → \(180 ÷ 60 = 3\)
Answer: 3 minutes

Example 3: Convert 7 feet to inches.
Step 1: 1 foot = 12 inches
Step 2: Multiply → \(7 × 12 = 84\)
Answer: 84 inches

Example 4: Convert 150 pounds to kg.
Step 1: 1 pound ≈ 0.454 kg
Step 2: Multiply → \(150 × 0.454 = 68.1\)
Answer: ≈ 68.1 kg

Example 5: Convert 2 liters to milliliters.
Step 1: 1 L = 1,000 mL
Step 2: Multiply → \(2 × 1,000 = 2,000\)
Answer: 2,000 mL

Remember these:

• Unit Conversion - Changing a measurement to a different unit.
• Conversion Factor - How many of one unit equals another (e.g., 1 m = 100 cm).
• Larger to Smaller → Multiply - Need more small units.
• Smaller to Larger → Divide - Need fewer big units.
• 1 km = 1,000 m - Metric length.
• 1 m = 100 cm - Metric length.
• 1 cm = 10 mm - Metric length.
• 1 kg = 1,000 g - Metric weight.
• 1 L = 1,000 mL - Metric volume.
• 1 foot = 12 inches - Imperial length.
• 1 yard = 3 feet - Imperial length.
• 1 inch = 2.54 cm - Exact conversion.
• 1 pound ≈ 0.454 kg - Weight conversion.
• 1 kg ≈ 2.2 pounds - Quick weight conversion.

Multiple Choice Questions

Answer these in the comment section. Choose the best answer for each item.

1. Convert 3.5 km to meters.

A. 350 m
B. 3,500 m
C. 35,000 m
D. 350,000 m

2. Convert 500 cm to meters.

A. 0.5 m
B. 5 m
C. 50 m
D. 500 m

3. Convert 2.5 hours to minutes.

A. 120 minutes
B. 150 minutes
C. 180 minutes
D. 200 minutes

4. Convert 10 pounds to kilograms (1 lb ≈ 0.454 kg).

A. 4.54 kg
B. 45.4 kg
C. 2.2 kg
D. 22 kg

5. Convert 6 feet to inches.

A. 60 inches
B. 66 inches
C. 72 inches
D. 78 inches