Percentage Change Calculator

Figure out how much something went up or down, in percentage terms, between an old value and a new one. If you just need to compare two numbers without an "old vs. new" order to them, the percent difference calculator is the better fit. Looking for what percentage one number is of another instead? Try the percentage calculator.

Enter Your Two Values

Change from V1 (old) to V2 (new)

Quick Reference

V1 → V2 Result
10 → 20100% increase
50 → 2550% decrease
-25 → 25200% increase
-25 → -50100% decrease

Result

Solution:

Share this calculation:

Enter V1 and V2, then hit Calculate to see the percentage change here.

How to Use This Calculator

  1. Put your starting number into V1. Think of this as the "before" or "old" value.
  2. Put your ending number into V2, the "after" or "new" value.
  3. Click Calculate. You'll see the percentage change, labeled clearly as either an increase or a decrease.
  4. Need to flip the direction and check the change the other way? Use the link that appears under your result to swap the new value into V1 for your next calculation.
  5. Copy or print your result using the buttons below the solution.

Practical Example / Formula Used

Percentage change compares how far a number moved relative to where it started:

% change = (V2 − V1) / |V1| × 100

Notice that's the absolute value of V1 in the denominator, not V1 itself. That detail matters whenever your starting number is negative skip it and you'll get a result with the wrong sign.

Here's a full walkthrough. Say a supplier's price moved from V1 = 628 to V2 = 226:

(226 − 628) / |628| × 100
= −402 / 628 × 100
= −64.0127% change
= 64.0127% decrease

And here's why the absolute value matters: going from V1 = −25 to V2 = 25 gives (25 − (−25)) / |−25| × 100 = 50/25 × 100 = 200% increase. Without the absolute value, that division by a negative number would flip the sign and give the wrong answer.

Why Use This Calculator?

  • It handles negative starting and ending values correctly, which is where a lot of manual percentage-change math goes wrong.
  • You get the full step-by-step solution, not just a final number, so you can follow along or double-check homework.
  • The result is labeled as an increase or decrease automatically, so there's no second-guessing what a negative percentage means.
  • Share links make it easy to send someone the exact numbers you calculated with.

Key Factors / Variables Explained

V1 - the starting, "old," or original value you're measuring the change from.

V2 - the ending, "new," or final value you're comparing to.

Increase vs. decrease - a positive percentage change means V2 is larger than V1 (an increase). A negative one means V2 is smaller (a decrease). This calculator flips negative results into a plain-language "decrease" so you don't have to do that translation yourself.

Order matters - percentage change from A to B is not the same as from B to A, because the denominator (the "original" value) changes. Going from 3.5 to 2.625 is a 25% decrease, but going from 2.625 back to 3.5 is a 33.33% increase, even though it's the same two numbers.

Frequently Asked Questions

Percentage change assumes one number is the "before" and the other is the "after," so the order you plug them in matters. Percent difference is used when neither number is really the starting point you're just comparing two values side by side, and it treats them symmetrically.

V1 is the reference point the change is measured against, so it needs to stay a positive-sized denominator regardless of its sign. If you used V2's absolute value instead, or neither, a negative starting value could flip an actual increase into what looks like a decrease.

Yes, easily. Going from 10 to 30 is a 200% increase, since the value tripled. There's no upper limit on how large an increase can get in percentage terms.

Percentage change isn't defined in that case, since you'd be dividing by zero. Going from nothing to something isn't really expressible as a percentage of the original amount, because there was no original amount to begin with.

It can, yes, especially for big swings. Dropping from 100 to 50 is a 50% decrease, but climbing back from 50 to 100 is a 100% increase. Same two numbers, very different percentages, because each calculation measures the change relative to a different starting point.

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