Unit Conversion (Grade 5)
Unit conversion means changing a measurement from one unit to another without changing its actual value. In Class 5, you learn to convert between units of length, weight (mass), capacity (volume), and time.
India uses the metric system, where units are related by powers of 10 — making conversions easy with multiplication and division.
Being able to convert units is essential for solving real-life problems involving distances, weights of groceries, volumes of liquids, and time calculations.
What is Unit Conversion - Class 5 Maths (Measurement)?
Unit conversion is the process of expressing a given quantity in a different unit of measurement. The value remains the same; only the unit changes.
Key principle:
- To convert from a larger unit to a smaller unit, multiply.
- To convert from a smaller unit to a larger unit, divide.
Unit Conversion (Grade 5) Formula
Length Conversions:
| Conversion | Relation |
|---|---|
| 1 km | = 1,000 m |
| 1 m | = 100 cm |
| 1 cm | = 10 mm |
| 1 m | = 1,000 mm |
| 1 km | = 1,00,000 cm |
Weight (Mass) Conversions:
| Conversion | Relation |
|---|---|
| 1 kg | = 1,000 g |
| 1 g | = 1,000 mg |
| 1 quintal | = 100 kg |
| 1 tonne | = 1,000 kg |
Capacity (Volume) Conversions:
| Conversion | Relation |
|---|---|
| 1 litre (L) | = 1,000 mL |
| 1 kL (kilolitre) | = 1,000 L |
Solved Examples
Example 1: Example 1: Kilometres to Metres
Problem: Convert 3.5 km to metres.
Solution:
Step 1: 1 km = 1,000 m
Step 2: 3.5 km = 3.5 × 1,000 = 3,500 m
Answer: 3.5 km = 3,500 m
Example 2: Example 2: Grams to Kilograms
Problem: Ria bought 2,500 g of rice. Express this in kilograms.
Solution:
Step 1: 1 kg = 1,000 g (smaller to larger → divide)
Step 2: 2,500 ÷ 1,000 = 2.5 kg
Answer: 2,500 g = 2.5 kg
Example 3: Example 3: Millilitres to Litres
Problem: A bottle contains 750 mL of juice. Express this in litres.
Solution:
Step 1: 1 litre = 1,000 mL
Step 2: 750 ÷ 1,000 = 0.75 L
Answer: 750 mL = 0.75 litres
Example 4: Example 4: Metres to Centimetres
Problem: Aman's classroom is 8.5 m long. Convert this to centimetres.
Solution:
Step 1: 1 m = 100 cm
Step 2: 8.5 × 100 = 850 cm
Answer: 8.5 m = 850 cm
Example 5: Example 5: Adding Different Units
Problem: Add 2 km 300 m and 1 km 750 m.
Solution:
Step 1: Convert everything to metres: 2 km 300 m = 2,300 m; 1 km 750 m = 1,750 m
Step 2: Add: 2,300 + 1,750 = 4,050 m
Step 3: Convert back: 4,050 m = 4 km 50 m
Answer: 4 km 50 m
Example 6: Example 6: Subtracting Weights
Problem: Priya has 5 kg 200 g of flour. She uses 1 kg 750 g. How much flour remains?
Solution:
Step 1: Convert to grams: 5 kg 200 g = 5,200 g; 1 kg 750 g = 1,750 g
Step 2: Subtract: 5,200 − 1,750 = 3,450 g
Step 3: Convert back: 3,450 g = 3 kg 450 g
Answer: 3 kg 450 g of flour remains.
Example 7: Example 7: Tonne to Kilograms
Problem: A truck carries 2.5 tonnes of goods. Convert this to kilograms.
Solution:
Step 1: 1 tonne = 1,000 kg
Step 2: 2.5 × 1,000 = 2,500 kg
Answer: 2.5 tonnes = 2,500 kg
Example 8: Example 8: Mixed Capacity Problem
Problem: Kavi has 3 litres 500 mL of milk. He gives away 1 litre 800 mL. How much milk is left?
Solution:
Step 1: Convert: 3 L 500 mL = 3,500 mL; 1 L 800 mL = 1,800 mL
Step 2: Subtract: 3,500 − 1,800 = 1,700 mL
Step 3: Convert back: 1,700 mL = 1 L 700 mL
Answer: 1 litre 700 mL of milk is left.
Example 9: Example 9: Centimetres to Millimetres
Problem: A pencil is 17.5 cm long. Express this in millimetres.
Solution:
Step 1: 1 cm = 10 mm
Step 2: 17.5 × 10 = 175 mm
Answer: 17.5 cm = 175 mm
Example 10: Example 10: Comparing Lengths
Problem: Which is longer: 3 km 200 m or 3,150 m?
Solution:
Step 1: Convert 3 km 200 m to metres: 3 × 1,000 + 200 = 3,200 m
Step 2: Compare: 3,200 m > 3,150 m
Answer: 3 km 200 m is longer.
Key Points to Remember
- The metric system is based on powers of 10.
- Larger to smaller unit → multiply. Smaller to larger unit → divide.
- Length: km → m (×1,000), m → cm (×100), cm → mm (×10).
- Weight: tonne → kg (×1,000), kg → g (×1,000), g → mg (×1,000).
- Capacity: kL → L (×1,000), L → mL (×1,000).
- Always convert to the same unit before adding, subtracting, or comparing.
- Convert back to mixed units for the final answer when required.
Practice Problems
- Convert 4.75 km to metres.
- Express 3,250 g in kilograms and grams.
- Aditi has 2 L 400 mL of water. She drinks 650 mL. How much is left?
- Add: 5 km 600 m + 3 km 850 m. Express in km and m.
- A rope is 15 m 30 cm long. Express this in centimetres.
- Convert 6,500 mL to litres.
- A bag weighs 3.25 kg. Express this weight in grams.
- Which is heavier: 2 kg 100 g or 2,050 g?
Frequently Asked Questions
Q1. What is unit conversion?
Unit conversion means changing a measurement from one unit to another while keeping the same value. For example, 2 km = 2,000 m — the distance is the same, only the unit changes.
Q2. When do you multiply and when do you divide?
Multiply when converting from a larger unit to a smaller unit (km to m, kg to g). Divide when converting from a smaller unit to a larger unit (cm to m, g to kg).
Q3. Why is the metric system easier for conversions?
The metric system uses powers of 10 (10, 100, 1000), so converting only requires moving the decimal point. Other systems (like feet and inches) use irregular multipliers.
Q4. How do you add measurements in different units?
First convert both measurements to the same unit. Then add. Finally, convert back to mixed units if needed. For example, 2 km 500 m + 800 m = 2,500 + 800 = 3,300 m = 3 km 300 m.
Q5. What is the relationship between litres and cubic centimetres?
1 litre = 1,000 cm³ (or 1,000 mL). This is useful when calculating the capacity of containers using volume formulas.
Q6. How many milligrams are in 1 kilogram?
1 kg = 1,000 g, and 1 g = 1,000 mg. So 1 kg = 1,000 × 1,000 = 10,00,000 mg (10 lakh milligrams).
Q7. What is a quintal?
A quintal is a unit of weight used in India, equal to 100 kg. It is commonly used in agriculture to measure crop yields.
Q8. How do you convert metres to kilometres?
Divide by 1,000. For example, 4,500 m = 4,500 ÷ 1,000 = 4.5 km.
Related Topics
- Converting Units of Length (Grade 4)
- Converting Units of Weight (Grade 4)
- Perimeter (Grade 5)
- Area (Grade 5)
- Area of Triangle (Grade 5)
- Area of Parallelogram (Grade 5)
- Introduction to Volume
- Volume of Cuboid
- Volume of Cube
- Volume Word Problems (Grade 5)
- Area of Irregular Shapes
- Perimeter Word Problems (Grade 5)
