The metric system is one of the most straightforward measurement systems (compared to customary units), but many students still struggle with converting between units like kilometers, meters, and centimeters. The key? Understanding place value, moving the decimal, and knowing when to multiply or divide.
In this post, we’ll learn how to convert metric units for length, mass, and capacity using easy-to-follow steps and examples. You’ll also find helpful practice ideas and printable resources to make teaching metric conversions easier.
What Are Metric Units?
The metric system is based on powers of 10, which makes it predictable and easy to use.
Each metric unit includes a base unit, with prefixes that show how big or small a measurement is compared to the base.
| Measurement Type | Base Unit | Examples of Units |
| Length | meter (m) | kilometer, centimeter, millimeter |
| Mass | gram (g) | kilogram, milligram |
| Capacity | liter (L) | kiloliter, milliliter |
General Rule: How to Convert Metric Units
To convert metric units:
- Multiply when going from a larger unit to a smaller unit
- Divide when going from a smaller unit to a larger unit
Think of it as zooming in or zooming out. When you zoom in (large to small), everything gets bigger, so you multiply. When you zoom out (small to large), things get smaller, so you divide.
How to Convert Metric Units of Length
We use metric units of length to measure how long or far something is. Some examples of using metric units of length are reading maps, running a marathon, or measuring someone’s height.
Metric Units of Length:
- Kilometer (km) = 1,000 meters
- Meter (m) = base unit
- Centimeter (cm) = 1/100 of a meter
- Millimeter (mm) = 1/1,000 of a meter
| Metric Units of Length Conversion |
| 1 kilometer (km) = 1,000 meters 1 meter (m) = 100 centimeters (cm) 1 meter = 1,000 millimeters |
Large Unit to Small Unit Example: Kilometers to Meters
Problem: Convert 5 kilometers to meters.
Step 1: Check the conversion. 1 kilometer = 1,000 meters
Step 2: Since you are converting from a large unit to a small unit, multiply. Multiply → 5 × 1,000 = 5,000
Answer: 5 kilometers = 5,000 meters
Small Unit to Large Unit Example: Millimeters to Meters
Problem: Convert 2,000 millimeters to meters.
Step 1: Check the conversion. 1 meter = 1,000 millimeters
Step 2: Since you are converting from a small unit to a large unit, divide. Divide → 2,000 ÷ 1,000 = 2
Answer: 2,000 millimeters = 2 meters
Our Metric Conversion Worksheets are a great way to reinforce these skills. It offers plenty of practice and guided notes.
How to Convert Metric Units of Mass
Metric units of mass measures how heavy something is. It’s a useful everyday skill, useful for measuring ingredients and weighing animals.
Metric Units of Mass:
- Kilogram (kg) = 1,000 grams
- Gram (g) = base unit
- Milligram (mg) = 1/1,000 of a gram
| Metric Units of Mass Conversion |
| 1 kilogram (kg) = 1,000 grams 1 gram (g) = 100 centigrams (cg) 1 gram = 1,000 milligrams (mg) |
Large Unit to Small Unit Example: Kilograms to Grams
Problem: Convert 3 kilograms to grams.
Step 1: First, check the conversion. 1 kilogram = 1,000 grams
Step 2: You are converting from a large unit to a small unit, so you multiply. Multiply → 3 × 1,000 = 3,000
Answer: 3 kilograms = 3,000 grams
Small Unit to Large Unit Example: Milligrams to Grams
Problem: Convert 7,500 milligrams to grams.
Step 1: Check the conversion. 1 gram = 1,000 milligrams
Step 2: Small unit to large unit means you divide.
Divide → 7,500 ÷ 1,000 = 7.5
Answer: 7,500 milligrams = 7.5 grams
How to Convert Metric Units of Capacity
Capacity measures how much liquid a container holds. These are usually used when cooking or doing experiments in a science lab.
Metric Units of Capacity:
- Kiloliter (kL) = 1,000 liters
- Liter (L) = base unit
- Milliliter (mL) = 1/1,000 of a liter
| Metric Units of Capacity Conversion |
| 1 kiloliter (kl) = 1,000 liters 1 liter (L) = 100 centiliters (cl) 1 liter = 1,000 milliliters (ml) |
Large Unit to Small Unit Example: Liters to Milliliters
Problem: Convert 6 liters to milliliters.
Step 1: 1 liter = 1,000 milliliters
Step 2: Multiply → 6 × 1,000 = 6,000
Answer: 6 liters = 6,000 milliliters
Small Unit to Large Unit Example: Milliliters to Liters
Problem: Convert 2,500 milliliters to liters.
Step 1: 1 liter = 1,000 milliliters
Step 2: Divide → 2,500 ÷ 1,000 = 2.5
Answer: 2,500 milliliters = 2.5 liters
How to Convert Metric Units Using a Conversion Chart
A metric conversion chart is a powerful visual that helps students understand how to move the decimal point. Use this sequence:
kilo → hecto → deka → base unit → deci → centi → milli
The base unit refers to grams, meters, and liters, depending on the unit of measure being converted.
Each step left or right is 10 times bigger or smaller than the next. Students can count the steps and move the decimal accordingly.
Below are examples of how to use this conversion chart.
Example 1: Convert 2.5 Kilometers to Meters
Use the metric conversion line:
kilo → hecto → deka → base unit (meter)
You’re moving from kilometers (kilo) to meters (base unit), so you move to the right.
Step 1: Count how many steps to the right on the conversion chart:
- kilo → hecto → deka → meter = 3 steps
Step 2: Move the decimal point 3 places to the right:
- 2.5 → 25 → 250 → 2,500
Answer: 2.5 kilometers = 2,500 meters
Example 2: Convert 450 Centimeters to Meters
Now let’s go from centi to base unit (meter), so you move the decimal place to the left.
Step 1: Count how many steps to the left:
- meter ← deci ← centi = 2 steps
Step 2: Move the decimal 2 places to the left:
- 450 → 45.0 → 4.5
Answer: 450 centimeters = 4.5 meters
Wrap Up: Converting Metric Units of Measure
Once students understand how to convert metric units by multiplying and dividing powers of ten, all it takes is for them to practice and master converting. The metric system’s logic and consistency make it one of the easiest systems to learn, especially when paired with hands-on practice and visual supports.
Start by introducing units in context, guide students through each step, and offer regular and extended practice to apply their skills.
Ready to simplify your planning? Download our Metric Units Conversion Worksheets for engaging, no-prep materials that help students build confidence through guided practice.
Click here to grab your printable metric units worksheets → Check it out here
Make conversions click for you and your students!
