A percentage increase is found by taking the difference between a new, larger value and an original, smaller value, dividing this difference by the original value and multiplying by 100. The multiplication by 100 converts the decimal value to a percentage.
If the new value is larger than the original value, the change represents a percentage increase. If the new value is smaller than the original value, the change represents a percentage decrease. The formula provided works for both cases; however, the difference between the new value and the original value will dictate whether the percentage change is an increase or a decrease.