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CC. Which metric unit should you use?

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What are metric units of measurement?

Metric units of measurement are a system of measuring length, mass (weight), and capacity (liquid volume) using powers of ten. The most common units you will use are meters (m), liters (L), and grams (g).

Examples:
  • Length: meter (m)
  • Mass: gram (g)
  • Capacity: liter (L)
Note

The metric system is used worldwide and makes measurement easier because each unit is based on tens.

How to choose the right metric unit

To choose the correct unit, think about the size of the object you are measuring and select the unit that makes sense without being too big or too small.

Steps:
  • Ask: What am I measuring? (length, mass, or capacity)
  • Estimate the size: small, medium, or large
  • Pick the best unit: millimeter (mm), centimeter (cm), meter (m), kilometer (km), milliliter (mL), liter (L), gram (g), or kilogram (kg)
Note

Always pick a unit that keeps numbers easy to understand. Avoid very large or very small numbers when possible.

Common metric units and when to use them

Here are the metric units you may use for measuring length, mass, and capacity. Choosing the right unit depends on the size of the object being measured:

Metric Units List:
  • Length: millimeter (mm) for very tiny lengths, centimeter (cm) for small objects, decimeter (dm) sometimes for classroom measurements, meter (m) for people, furniture, or rooms, dekameter (dam) for playgrounds or fields, hectometer (hm) for larger land areas, kilometer (km) for distances between towns or cities.
  • Mass: milligram (mg) for very light items like medicine, centigram (cg) and decigram (dg) for small laboratory use, gram (g) for everyday light objects, dekagram (dag) and hectogram (hg) sometimes in science or food measurement, kilogram (kg) for people, pets, and heavier objects, metric ton (t) for very heavy things like cars or trucks.
  • Capacity: milliliter (mL) for small amounts like a spoonful of liquid, centiliter (cL) and deciliter (dL) sometimes for beverages, liter (L) for bottles, pitchers, and larger containers, dekaliter (daL) and hectoliter (hL) sometimes for large quantities like in industry, kiloliter (kL) for very large volumes such as tanks or pools.
Note

Remember: the metric system is based on tens, so each step up or down changes the unit by a factor of 10. Think of real-life examples: a grain of rice weighs about 25 milligrams, a paperclip about 1 gram, a bottle of water about 500 milliliters, and the distance across a city might be several kilometers.

Examples of using the right unit

Look at these examples to see how different units are chosen depending on what is being measured:

Examples:
  • The length of a pencil → 15 centimeters (cm)
  • The weight of an apple → 150 grams (g)
  • The amount of milk in a carton → 1 liter (L)
  • The distance between two cities → 120 kilometers (km)
Note

Ask yourself: does the unit match the size of the object? If yes, you chose correctly.

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