Calculate percentage increase from initial (old) value to final (new) value:
Calculate final (new) value from initial (old) value and percentage increase:
The percentage increase/decrease from initial value (Vinitial) to final value (Vfinal) is equal to the initial and final values difference divided by the initial value times 100%:
Price percentage increase from initial value of $1000 to final value of $1200 is caluclated by:
Price percentage increase from initial value of $1000 to final value of $800 is caluclated by:
So
percentage decrease = 20%
The difference d is equal to the initial value Vinitial times the percentage increase/decrease p divided by 100:
The final value Vfinal is equal to the initial value Vinitial plus the difference d:
Vfinal = Vinitial + d