- How do I calculate percent change?
- Subtract the old value from the new one, divide by the old value, and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25, so it's a 25% increase. A negative result is a decrease: from 100 to 80 is (80 − 100) ÷ 100 × 100 = −20%. The one rule people break is the denominator. It's always the value you started from, never the new one and never the average.
- Percent change or percent difference?
- Use percent change when there's a before and an after: last year's price and this year's, your old salary and your new one. The order matters, and the answer has a sign. Use percent difference when two values are just being compared and neither one came first, like two lab measurements or two stores' prices. That formula divides by the average of the two and is the same whichever way round you type them. Microapp has a separate Percent Difference Calculator for that.
- Why isn't going back the same percent?
- Because the starting point changes. 80 to 100 is +25%, since 20 is a quarter of 80. Going back, 100 to 80 is only −20%, since 20 is a fifth of 100. The gap grows with the size of the move: a stock that falls 50% needs to rise 100% to get back where it was, and a 10% raise followed by a 10% pay cut leaves you 1% below where you started (×1.1 × ×0.9 = ×0.99). That's why the calculator always shows the reverse line.
- What's the percent change from zero?
- There isn't one. The formula divides by the starting value, and you can't divide by zero, so going from 0 to 50 has no percent change. It isn't 100% and it isn't infinite. The honest way to describe it is the absolute change: it went up by 50. Plenty of tools show NaN, Infinity, or an error here; this one says it plainly and still gives you the change.
- How does percent change work with negative numbers?
- Divide by the size of the starting value, ignoring its sign. A loss that shrinks from −50 to −25 is (−25 − (−50)) ÷ |−50| × 100 = +50%, an increase, which matches what happened: the number went up. Without the absolute value you'd get −50%, which reads as the loss getting worse. Spreadsheets using =(B1−A1)/A1 make exactly that mistake. When a value crosses zero, like profit turning into a loss, the math still works but the percent is hard to read, so the calculator flags it.
- Is percent change the same as percentage points?
- No, and news stories mix them up constantly. If an interest rate goes from 3% to 4%, it rose by 1 percentage point, which is the plain subtraction. The percent change is (4 − 3) ÷ 3 × 100 = 33.33%, because the rate itself grew by a third. Both are correct; they answer different questions. When the values you're comparing are already percentages, say which one you mean.
- Can a percent change be more than 100%?
- Going up, yes, with no ceiling. 20 to 60 is a 200% increase, because it tripled (×3). Going down, a positive value bottoms out at −100%, which means it fell all the way to zero. You can only see a decrease past −100% when the value crosses into negative numbers, like a profit of 100 turning into a loss of 50, which is −150%.
- What does the multiplier tell me?
- It's the new value divided by the old one, and it's often easier to work with than the percent. ×1.25 means a 25% increase, ×0.8 means a 20% decrease, ×1 means nothing changed. Multipliers chain by multiplying, which percents don't: two years of +10% growth is ×1.1 × ×1.1 = ×1.21, a 21% total increase, not 20%. For growth across many years, a CAGR calculator turns the total multiplier into a yearly rate.
- Is what I type saved or sent anywhere?
- No. The calculation runs in your browser. Nothing is sent to a server or stored, and closing the tab clears it.
