Measure Length, Mass, and Capacity

Measurement lets us describe the world in numbers. We measure three key attributes: length (how long), mass (how heavy), and capacity (how much a container holds). In the US we use two systems side by side: customary units (inches, pounds, cups) and metric units (centimeters, grams, liters). Both are correct — pick the unit that fits the size of the object.

Length

• Use a ruler for short lengths — inches (in) on one side, centimeters (cm) on the other.
• Use a tape measure for longer lengths — feet (ft) and yards (yd), or meters (m).
• Long distances: miles (mi) for US road signs; kilometers (km) for science and most countries.
• Anchors: a pencil is about 6 in or 15 cm. A door is about 7 ft or 2 m. A running track is 1 mi or about 1.6 km.

Mass

• Use a kitchen scale or balance scale to find mass (or weight).
• Small objects: ounces (oz) or grams (g). Larger objects: pounds (lb) or kilograms (kg).
• Anchors: an apple is about 6 oz or 170 g. A bag of sugar is about 5 lb or 2.3 kg. 1 lb ≈ 454 g; 1 kg ≈ 2.2 lb.

Capacity

• Capacity is how much liquid a container can hold.
• Use a measuring cup (cups, pints, quarts, gallons) or a graduated cylinder (milliliters, liters).
• Anchors: a drinking glass is about 1 cup or 240 mL. A milk jug holds 1 gallon or about 3.8 L. A teaspoon holds 5 mL.