What is the standard formula for percent change (percent increase or decrease)?

• A. Percent Change = (New - Original) / Original
• B. Percent Change = Original / New
• C. Percent Change = (Original - New) / 100
• D. Percent Change = (New + Original) / Original

Answer: (A)

Percent change measures how much a value has changed relative to its starting amount, expressed as a percentage. To compute it, take the difference between the new value and the original value, divide by the original value, and then multiply by 100 to turn the ratio into a percentage. So the standard formula is percent change = [(new value − original value) / original value] × 100%. If the result is positive, there’s an increase; if negative, a decrease. For example, original 80, new 100 gives (100 − 80)/80 = 0.25, so 25% increase. If new is 60, you get (60 − 80)/80 = −0.25, i.e., a 25% decrease.

The other approaches don’t measure change relative to the starting point: swapping the denominator, dividing by 100 instead of the original, or combining the numbers in a way that doesn’t reflect how much the original value has changed.