Weight and Mass

Weight tells you how heavy something is. You measure weight using units like pounds and ounces or kilograms and grams. Math helps you compare weights and figure out how much things weigh together.

Units of Weight

In the United States, people use pounds and ounces. There are 16 ounces in one pound. A loaf of bread weighs about 1 pound. A car weighs about 3,000 pounds.

Scientists often use grams and kilograms. There are 1,000 grams in one kilogram. A paperclip weighs about 1 gram. A textbook weighs about 1 kilogram.

Comparing and Adding Weights

You can use math to compare weights. An elephant weighs about 12,000 pounds. A mouse weighs about 1 ounce. The elephant weighs much, much more.

You can also add weights together. If your backpack weighs 5 pounds and you add a book that weighs 2 pounds, your backpack now weighs 7 pounds.

Fun Facts

• A blue whale can weigh over 300,000 pounds, making it the heaviest animal ever.
• On the Moon, you would weigh about one-sixth of what you weigh on Earth.
• A gallon of water weighs about 8.3 pounds.

Did You Know?

Weight and mass are not exactly the same thing. Mass is how much stuff is in an object. Weight is how hard gravity pulls on it. Your mass stays the same on the Moon, but your weight changes!