Units of Measurement | Fourth Grade
Complete Notes & Formulas
1. Choose the Appropriate Metric Unit of Measure
Definition: Selecting the right metric unit means choosing the most suitable unit (mm, cm, m, km, g, kg, ml, L) based on the size of what you're measuring.
📏 Three Types of Measurement:
1. Length/Distance
- Millimeter (mm): Thickness of a coin, width of a fingernail
- Centimeter (cm): Length of a pencil, width of a book
- Meter (m): Height of a door, length of a room
- Kilometer (km): Distance between cities, long roads
2. Mass/Weight
- Milligram (mg): Medicine, tiny grains
- Gram (g): Small objects, paper clip, candy
- Kilogram (kg): Bag of rice, person's weight, furniture
3. Volume/Capacity
- Milliliter (ml): Spoonful of medicine, eye drops
- Liter (L): Water bottle, milk carton, juice jug
- Kiloliter (kL): Swimming pool, water tank
2. Compare and Convert Metric Units of Length
Definition: Converting length means changing from one unit to another (like cm to m) and comparing means determining which measurement is larger or smaller.
📐 Length Conversion Chart:
| Unit | Symbol | Conversion |
|---|---|---|
| Kilometer | km | 1 km = 1000 m |
| Meter | m | 1 m = 100 cm |
| Centimeter | cm | 1 cm = 10 mm |
| Millimeter | mm | Smallest unit |
🔑 Key Conversion Formulas:
1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
📝 Conversion Rules:
- Bigger to Smaller Unit: Multiply (km→m: ×1000, m→cm: ×100, cm→mm: ×10)
- Smaller to Bigger Unit: Divide (mm→cm: ÷10, cm→m: ÷100, m→km: ÷1000)
✏️ Examples:
Convert 3 km to meters:
3 km = 3 × 1000 = 3000 m
Convert 250 cm to meters:
250 cm = 250 ÷ 100 = 2.5 m
Convert 45 mm to cm:
45 mm = 45 ÷ 10 = 4.5 cm
3. Compare and Convert Metric Units of Mass
Definition: Mass measures how heavy an object is. Converting mass means changing between grams and kilograms.
⚖️ Mass Conversion Chart:
| Unit | Symbol | Conversion |
|---|---|---|
| Kilogram | kg | 1 kg = 1000 g |
| Gram | g | 1 g = 1000 mg |
| Milligram | mg | Smallest unit |
🔑 Key Conversion Formula:
1 kg = 1000 g
📝 Conversion Rules:
- Kilograms to Grams: Multiply by 1000 (kg → g: ×1000)
- Grams to Kilograms: Divide by 1000 (g → kg: ÷1000)
- Grams to Milligrams: Multiply by 1000 (g → mg: ×1000)
✏️ Examples:
Convert 5 kg to grams:
5 kg = 5 × 1000 = 5000 g
Convert 3500 g to kilograms:
3500 g = 3500 ÷ 1000 = 3.5 kg
Convert 0.75 kg to grams:
0.75 kg = 0.75 × 1000 = 750 g
4. Compare and Convert Metric Units of Volume
Definition: Volume (or capacity) measures how much liquid a container can hold. Converting volume means changing between milliliters and liters.
🥤 Volume Conversion Chart:
| Unit | Symbol | Conversion |
|---|---|---|
| Kiloliter | kL | 1 kL = 1000 L |
| Liter | L | 1 L = 1000 ml |
| Milliliter | ml | Smallest common unit |
🔑 Key Conversion Formula:
1 L = 1000 ml
📝 Conversion Rules:
- Liters to Milliliters: Multiply by 1000 (L → ml: ×1000)
- Milliliters to Liters: Divide by 1000 (ml → L: ÷1000)
- Kiloliters to Liters: Multiply by 1000 (kL → L: ×1000)
✏️ Examples:
Convert 4 L to milliliters:
4 L = 4 × 1000 = 4000 ml
Convert 2500 ml to liters:
2500 ml = 2500 ÷ 1000 = 2.5 L
Convert 0.25 L to milliliters:
0.25 L = 0.25 × 1000 = 250 ml
5. Metric Mixed Units
Definition: Mixed units use two different units together, like "2 kg 500 g" or "3 m 45 cm". Converting and calculating with mixed units requires careful attention.
📝 Understanding Mixed Units:
- Length: 2 m 35 cm means 2 meters + 35 centimeters
- Mass: 3 kg 250 g means 3 kilograms + 250 grams
- Volume: 1 L 500 ml means 1 liter + 500 milliliters
🔄 Converting Mixed Units to Single Unit:
- Step 1: Convert the larger unit to the smaller unit
- Step 2: Add the smaller unit value
- Step 3: Write the total in one unit
✏️ Examples - Mixed to Single Unit:
Example 1: Convert 3 m 45 cm to centimeters
Solution:
3 m = 3 × 100 = 300 cm
300 cm + 45 cm = 345 cm
Answer: 345 cm
Example 2: Convert 2 kg 750 g to grams
Solution:
2 kg = 2 × 1000 = 2000 g
2000 g + 750 g = 2750 g
Answer: 2750 g
Example 3: Convert 4 L 250 ml to milliliters
Solution:
4 L = 4 × 1000 = 4000 ml
4000 ml + 250 ml = 4250 ml
Answer: 4250 ml
✏️ Examples - Single to Mixed Units:
Example 1: Convert 3500 g to kg and g
Solution:
3500 ÷ 1000 = 3 remainder 500
Answer: 3 kg 500 g
Example 2: Convert 485 cm to m and cm
Solution:
485 ÷ 100 = 4 remainder 85
Answer: 4 m 85 cm
➕ Adding and Subtracting Mixed Units:
- Add/subtract the smaller units first
- If result ≥ conversion value, carry to larger unit
- Add/subtract the larger units
Example: 2 kg 600 g + 1 kg 750 g
Grams: 600 + 750 = 1350 g = 1 kg 350 g
Kilograms: 2 + 1 + 1 (carry) = 4 kg
Answer: 4 kg 350 g
Metric Units Quick Reference Chart
| Measurement Type | Units (Small to Large) | Key Conversion |
|---|---|---|
| Length | mm → cm → m → km | ×10, ×100, ×1000 |
| Mass | mg → g → kg | ×1000, ×1000 |
| Volume | ml → L → kL | ×1000, ×1000 |
📐 Essential Conversion Formulas:
1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
1 kg = 1000 g
1 L = 1000 ml
1 g = 1000 mg
💡 Memory Tips:
- Bigger to Smaller: Multiply (move decimal right)
- Smaller to Bigger: Divide (move decimal left)
- Remember 1000: Most metric conversions use 1000
📚 Fourth Grade Units of Measurement - Complete Study Guide
Master these metric conversion skills for math excellence! ✨