The familiar units of measurement used in the United States, pounds, gallons and degrees Fahrenheit, come from old English custom. Since, with a couple of exceptions, the rest of the world uses the metric system of kilos, liters and degrees Celsius, you may find yourself needing to convert units from one system to the other. While scientists developed both Fahrenheit and Celsius to deal with body heat, the weather and other everyday uses of temperature, the two units have differences. You can convert between them with a simple four-function calculator.

Key in 23 on your calculator. This represents temperature in degrees Celsius.

Multiply by 9 and divide by 5.

Add 32. The result is degrees Fahrenheit.

#### Tip

Water determines the Celsius scale. At 0 Celsius water freezes, and at 100 degrees it boils. If you know that water turns to ice at 32 degrees Fahrenheit and boils at 212 Fahrenheit, this will help you grasp how the two scales relate to each other.