Measurement with standard units
Measurement helps us find out how big, how heavy, or how much of something we have. When we all use the same units to measure, we can understand each other's measurements. These common units are called standard units.
Length
Length tells us how long something is from one end to the other. In the United States, we often use:
- Inches (in)
- Feet (ft) - 1 foot = 12 inches
- Yards (yd) - 1 yard = 3 feet
- Miles (mi) - 1 mile = 5,280 feet
In most other countries, people use the metric system:
- Millimeters (mm) - very small, about the thickness of a dime
- Centimeters (cm) - 1 cm = 10 mm (about the width of your pinky finger)
- Meters (m) - 1 m = 100 cm (about the height of a doorknob)
- Kilometers (km) - 1 km = 1,000 m (about how far you might walk in 10-15 minutes)
Weight/Mass
Weight tells us how heavy something is. In the United States, we often use:
- Ounces (oz)
- Pounds (lb) - 1 pound = 16 ounces
- Tons (T) - 1 ton = 2,000 pounds
In the metric system:
- Grams (g) - about the weight of a paperclip
- Kilograms (kg) - 1 kg = 1,000 g (about the weight of a textbook)
Capacity/Volume
Capacity tells us how much a container can hold. In the United States, we often use:
- Fluid ounces (fl oz)
- Cups (c) - 1 cup = 8 fluid ounces
- Pints (pt) - 1 pint = 2 cups
- Quarts (qt) - 1 quart = 2 pints
- Gallons (gal) - 1 gallon = 4 quarts
In the metric system:
- Milliliters (mL) - about a drop of water
- Liters (L) - 1 L = 1,000 mL (about a medium-sized water bottle)
Choosing the Right Unit
When measuring, it's important to choose a unit that makes sense for what you're measuring:
- We measure a pencil in inches or centimeters, not miles or kilometers.
- We measure the weight of a person in pounds or kilograms, not ounces or grams.
- We measure milk for a recipe in cups or milliliters, not gallons or liters.
Using the right unit makes our measurements more useful and easier to understand!