Find the percent increase or decrease between any two values — plus the symmetric percent difference, which is a different thing and often confused with it. The second tab works in reverse: enter a value and a percentage to see what it becomes after the increase or decrease.
Percent change is directional (old → new). Percent difference is symmetric — it compares two values without treating either as the starting point, so it gives the same answer both ways.
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The formula, worked out
Percent change = (new − old) / old × 100. Say a sneaker cost $80 last month and $100 today. The change is 100 − 80 = 20, and 20 / 80 × 100 = +25%. The direction matters: if the price falls back from $100 to $80, the change is −20 / 100 × 100 = −20%, not −25%, because the base is now the higher price.
Percent difference answers a different question — how far apart two values are with no before/after direction. It divides the gap by the average of the two: |100 − 80| / 90 × 100 ≈ 22.2%. Use it for comparing two prices side by side; use percent change when time passed between the values.
The classic gotcha: percentage changes do not cancel out. A −50% drop followed by a +50% rise leaves you at 75% of where you started ($100 → $50 → $75), because the rise is computed from the smaller base. Undoing a 50% loss takes a +100% gain.
Frequently asked questions
Percent change = (new value − old value) / old value × 100. Going from 80 to 100: (100 − 80) / 80 × 100 = +25%. Going from 100 to 80: (80 − 100) / 100 × 100 = −20%. Note the answers differ even though the values are the same — percent change always measures relative to the starting value.
Percent change is relative; percentage points are absolute. If an interest rate goes from 4% to 5%, that is a rise of 1 percentage point but a 25% percent change (1/4 of the original rate). News headlines often mix these up. The percentage point calculator on this site handles that comparison specifically.
Yes — increases have no upper limit. Going from 50 to 150 is a +200% change, and going from 10 to 1,000 is +9,900%. A decrease, however, can be at most −100%, which means the value dropped all the way to zero. A value cannot lose more than all of itself (unless it goes negative, where percent change becomes hard to interpret).
Because the second percentage is taken from a smaller base. Drop $100 by 50% and you have $50; raising $50 by 50% adds only $25, leaving $75. To undo a 50% drop you need a +100% rise. In general, undoing a p% decrease requires an increase of p / (1 − p/100) percent — this is the classic gotcha behind "the stock recovered" headlines.
Subtract the old price from the new one, divide by the old price, and multiply by 100. A grocery item going from $2.50 to $2.89 rose by (2.89 − 2.50) / 2.50 × 100 = 15.6%. Working the other way: a $1,200 rent with a 5% increase becomes 1,200 × 1.05 = $1,260 — the second tab of the calculator does exactly this.
Percent difference compares two values symmetrically, with no "before" and "after": |a − b| divided by the average of the two, times 100. Comparing 80 and 100 gives 20 / 90 × 100 ≈ 22.2% either way. Use percent difference to compare two simultaneous measurements (two prices, two lab results); use percent change when one value came before the other in time.