How to Calculate Decreased Percentages

A 20 percent off sale is a 20 percent decrease in price.

There are many scenarios in everyday life that involve decreases in percentages, such as a sale for 50 percent off of a normal price or an investment that has lost 10 percent of its value. In a percentage decrease, you start out with one number and end up with a smaller number after the original number has been reduced by a certain percentage. A percentage decrease can be difficult to recover from in financial situations because after an amount of money has decreased by a percentage, it must increase by a greater percentage to get back to the original amount.

Instructions

Calculating the Amount of a Known Percentage Decrease

1. Determine a starting number and percentage by which to decrease it. For this example, decrease $150 by 40 percent, which is similar to a sale of 40 percent off.

2. Convert 40 percent to a decimal by moving the decimal two places to the left and eliminating the percent sign. This leaves 0.4.

3. Multiply 0.4 by $150, which equals $60.

4. Subtract $60 from the original amount -- $150 minus $60 equals $90. This is the result of $150 decreased by 40 percent, or 40 percent off of $150.

Calculating a Percentage of a Known Amount Decrease

1. Determine a starting amount and a smaller amount that's a result of a percentage decrease. For this example, use $5,000 as a starting investment amount and $4,500 as the new amount after a loss.

2. Subtract the new amount from the original amount -- $5,000 minus $4,500 equals $500.

3. Divide the amount of decrease by the original amount -- $500 divided by $5,000 equals 0.1.

4. Move the decimal two places to the right and add the percent sign to convert to a percentage -- 0.1 becomes 10 percent. The percentage decrease from $5,000 to $4,500 is 10 percent.

References

• Minnesota State University, Moorhead: Percent Off, Increase and Decrease
• Cerritos College: Conversions Between Fractions, Decimals and Percent
• Math Is Fun: Percentage Change