Percentage increase tells you how much a value has grown, relative to where it started. It’s the same calculation whether you’re looking at a salary raise, a price hike, or a jump in website traffic.
The formula
percentage increase = ((new value − old value) ÷ old value) × 100If the result is negative, the value went down — that’s a percentage decrease, calculated with the exact same formula.
Worked example: a salary raise
Say your salary went from $60,000 to $66,000.
(66,000 − 60,000) ÷ 60,000 × 100 = 10%That’s a 10% raise.
Worked example: a price drop
A jacket’s price drops from $80 to $60.
(60 − 80) ÷ 80 × 100 = −25%A −25% change means the price decreased by 25%.
The mistake almost everyone makes
The most common error is dividing by the new value instead of the old one. Percentage change is always relative to where you started, not where you ended up — so the denominator is always the original value.
Another common trap: a 50% decrease followed by a 50% increase does not bring you back to the start. If a $100 item drops 50% to $50, a 50% increase from there only brings it to $75, because the second percentage is calculated on a smaller base.
Try it yourself
Our percentage calculator has a dedicated “% Change” tab that does this instantly — type in the old and new values and it computes the increase or decrease for you, entirely in your browser.