Question 1

What is the percent change formula?

Accepted Answer

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.

Question 2

What is the difference between percent change and percentage points?

Accepted Answer

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.

Question 3

Can percent change be more than 100%?

Accepted Answer

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).

Question 4

Why does −50% followed by +50% not get me back to the start?

Accepted Answer

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.

Question 5

How do I calculate a price increase in percent?

Accepted Answer

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.

Question 6

What is percent difference and when should I use it?

Accepted Answer

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.

Percent Change Calculator

The formula, worked out

More percentage and math tools

Frequently asked questions