Percentage Change Calculator
Compare an original value with a new value for directional increase or decrease, or compare two peer measurements using symmetric percentage difference.
Written and checked by TheToolNet Editorial Team · Last reviewed: September 20, 2026 · Editorial method
Calculate percentage change or difference
Percentage increase and decrease formula
Use directional change when one value is clearly the starting point. It covers salary increments, price changes, growth, decline, and shrinkage. From 80 to 100, the increase is 20/80 × 100 = 25%.
Percentage difference formula
Use symmetric difference for two peer measurements when neither is the baseline. Swapping a and b leaves the result unchanged. This is not the same question as percentage change.
Frequently asked questions
How do I calculate salary increment percentage?
Choose directional change, use old salary as the original, and new salary as the new value.
How do I calculate shrinkage percentage?
Choose directional change, enter the starting size or quantity first and the reduced value second.
Can percentage change start from zero?
No finite relative percentage exists because the formula would divide by zero. Report the absolute change or choose another baseline.
How do I recover the old value?
Use the reverse percentage calculator.