Percentage Change Calculator | Increase or Decrease

How the Percentage Change Formula Works

The formula divides the difference between two values by the original value:

Percentage Change = ((New Value − Original Value) / Original Value) × 100

The calculator needs an original value greater than 0. The new value can be negative.

A positive result means the value increased. A negative result means it decreased. If the result is exactly zero, the two values are identical.

Note that the original value cannot be zero — dividing by zero is undefined, so "percentage change from zero" has no mathematical meaning. If your starting point is 0, you'd need a different measure like absolute difference.

Percentage Change vs. Percentage Difference

These two calculations answer different questions:

Percentage change has a clear direction — it tells you how much a value moved from an original to a new value. The order matters: going from 100 to 150 is a 50% increase, but going from 150 to 100 is a decrease of about 33.3%.

Percentage difference compares two values without assigning one as the starting point. It divides the absolute difference by the average of both values. This is useful when neither value is the "original" — for example, comparing prices between two stores.

If you know which value came first in time or priority, use percentage change. If you're comparing two parallel values, use percentage difference.

When You'd Use Percentage Change

Percentage change measures growth, decline, or movement between two points:

Finance: Tracking stock price movements, investment returns, revenue growth quarter over quarter, or year-over-year changes in expenses. A share moving from $80 to $96 is a 20% gain — much more meaningful than saying it went up "$16" if you're comparing it to a stock that moved from $800 to $816.

Business: Measuring sales performance, conversion rate shifts, customer churn changes, or cost fluctuations. Knowing that your customer acquisition cost dropped 12% is actionable; knowing it dropped $3.40 requires more context.

Education: Test score improvements, grade tracking, enrollment changes. Going from 65 to 78 on a test is a 20% improvement.

Daily life: Price changes at the grocery store, rent increases, salary negotiations, weight loss or gain. Converting absolute numbers to percentages makes it easier to judge whether a change is significant.

Handling Negative Numbers

The original value must be greater than 0, and a negative original value gives an error message. The new value can be negative: going from 40 to −20 is a 150% decrease, because the value fell by 60, which is 150% of 40.

This can feel counterintuitive with temperatures or debt. If your debt was $5,000 and is now $7,500, that's a 50% increase in debt — the number got larger, even though the financial impact is negative. The calculator reports the mathematical direction; interpreting what "up" or "down" means in your context is up to you.

An original value of zero gives an error message too. There's no valid percentage relationship to a zero starting point.

Frequently Asked Questions

What is the difference between percentage change and percentage points?

Percentage change measures the relative shift between two values (e.g., going from 50 to 75 is a 50% change). Percentage points measure the simple numerical difference between two percentages (e.g., an interest rate moving from 3% to 5% increased by 2 percentage points, but the percentage change is about 66.7%).

Why can't I calculate percentage change from zero?

The formula divides by the original value. Dividing by zero is undefined in mathematics — there's no meaningful way to express "how much larger something is compared to nothing." If your starting point is zero, use absolute difference instead.

Does the order of the values matter?

Yes. Percentage change is directional. Going from 100 to 150 is a +50% increase. Going from 150 to 100 is a decrease of about 33.3%. Always enter the earlier or baseline value as the "Original" and the later or comparison value as "New."

How do I reverse a percentage change?

A common mistake is thinking a 20% increase followed by a 20% decrease gets you back to the starting point. It doesn't. If 100 increases by 20%, you get 120. A 20% decrease from 120 is 96, not 100. To reverse a percentage change, use the formula: reverse % = -(change / (100 + change)) × 100.

Can the percentage change be more than 100%?

Absolutely. If a value triples (e.g., 50 to 150), that's a 200% increase. There's no upper limit. Decreases can also exceed 100% when the value crosses zero — for example, going from 50 to −50 is a 200% decrease.

How does this handle negative original values?

It doesn't accept them: the original value must be greater than 0, and a negative original value gives an error message. The new value can be negative, so going from 50 to −50 is a 200% decrease.