The Celsius scale was created by Anders Celsius, a Swedish scientist who lived in the early 18th century. The scale is based on two fixed points -- 0 degrees is the point at which water freezes, while 100 degrees is the point at which water boils. Exact conversion of a Fahrenheit temperature to its Celsius equivalent is a straightforward equation. However, if an estimate within a few degrees is sufficient, an even easier way to convert is possible.

## Exact Conversion Method

Multiply the temperature in Celsius by 9. For example, if the temperature is 10, multiply 10 by 9. The result will be 90.

Divide the result in Step 1 by 5. For example, if the result was 90, divide 90 by 5. The result will be 18.

Add 32 to the result in Step 2. If the result was 18, add 18 to 32. The result will be 50. This is the temperature in Fahrenheit.

## Quick Estimate Method

Enter the temperature in Celsius into a calculator. Alternatively, hold the number in your head.

Multiply the temperature in Celsius by 2. For example, if the temperature in Celsius is 10, the result will be 20.

Add 30 to the result in Step 2. For example, if the result was 20, add 20 to 30. The result will be 50. This result is an estimate of the temperature in Fahrenheit; in this particular example, it also happens to be the same as the exact conversion.