What is the percentage change formula?

Percentage change = ((To − From) / |From|) × 100. A positive result means an increase; a negative result means a decrease. The absolute value of the original is used so the direction is always determined by the sign of (To − From).

What is the difference between percentage change and percentage difference?

Percentage change measures how a single value moves from one point to another (directional). Percentage difference compares two values symmetrically with no direction implied, using the average of the two as the denominator.

Why does the calculator show an error when the From value is 0?

Division by zero is undefined. If the starting value is 0, percentage change cannot be calculated mathematically. Enter any non-zero starting value.

How is "X is what % of Y" different from percentage change?

It answers "what fraction is X of Y, expressed as a percent?" using the formula (X / Y) × 100. There is no reference to a direction of change — it is purely a ratio.

Can I use negative numbers?

Yes. All three modes accept negative and decimal inputs. For example, a price drop from 200 to −50 is a 125% decrease.

Percentage Change Calculator

Name: Percentage Change Calculator
Availability: InStock
Author: Nham Vu

Enter two values to instantly see percentage change (increase or decrease), absolute difference, ratio, and the formula used. Three modes: Percentage Change, X is what % of Y, and What is X% of Y.

Percentage Calculator

Mode

From (original value)

To (new value)

Enter two values and click Calculate

Result, formula, and breakdown will appear here

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Summary

Enter two values to instantly see percentage change (increase or decrease), absolute difference, ratio, and the formula used. Three modes: Percentage Change, X is what % of Y, and What is X% of Y.

How it works

Select a mode from the tabs: Percentage Change, X is what % of Y, or What is X% of Y.
Enter the first value (From / X) in the top input field.
Enter the second value (To / Y) in the bottom input field.
Click Calculate to see the result, or click Reset to clear all fields.
Click Copy next to any result to copy the value to your clipboard.

Use cases

Measure revenue growth or decline between two financial periods.
Calculate a discount: what percentage off is the sale price vs. the original?
Determine what share one value is of a total, such as a test score out of total marks.
Quickly apply a known percentage to a base number, such as computing a tip or tax.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu