How to Calculate Percent Change

Math doesn't come easy to all of us, and with the use of calculators and spreadsheets, it sometimes seems as though we'll never have to add, subtract, multiply or divide on our own again.
Occasionally, though, it may be necessary to calculate percent change--a company's income one year to the next, a budget increase from quarter to quarter, population growth over a 10-year period. Here is a simple way to do this math.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• pen/pencil and scrap paper
• calculator

1. Take the old value and subtract it from the new value, then divide by the old value.

2. Multiply by 100. That number represents the percent change.

3. Here's an example:
   
   Brayton School had 16 teachers in 1998. The next year, there were 12. What is the percent change from 1998 to 1999?
   
   Take 16 and subtract 12. That's 4. Then divide 4 by 16. That's .25. Now mulitply by 100 and you get 25. That's the percent change. The number of teachers at Brayton School went down 25 percent from 1998 to 1999.

[csswenson]

on 6/19/2009 Alternatively, divide the recent period by the past period and subtract one, then multiply by 100: (RP/PP)-1*100. This equation is the same as above, just reformulated.

[brookema]

on 5/7/2009 thanks so much!

[zxd31]

on 4/1/2009 Even easier: New / Old - 1

[RickyRay]

on 8/14/2008 You got the formula right; however, you did not apply it correctly. You stated to subtract the first number (16) from the second number (12). This is 12 – 16, which equal -4. -4 divided by 16 = -.25. You’re confusing the reader by assuming they understand you reversed the numbers 16 and 12. The negative sign tells the person that there was a decrease, not an increase.