Loading page
About this tool
Work out percentage increase, decrease, percentage difference, percentage of a number and percentage points in one place.
Percentage change measures a before-and-after move as (new − old) ÷ |old| × 100, while percentage difference compares two values with no baseline as |a − b| ÷ their average × 100 — two different formulas that give two different answers for the same pair of numbers. This calculator covers both, plus percent of a number, X is what percent of Y, applying an increase or decrease, and the percentage-point gap between two rates. Each result is shown with the formula that produced it, so the answer can be checked rather than trusted.
Open Percentage Change and Difference Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Change, difference, percent of, what percent, apply a change and percentage points.
Every result displays the expression used, so it can be verified by hand.
Zero baselines, negative values and reverse changes return a plain explanation, never a bad number.
Subtract the old value from the new value, divide by the absolute value of the old value, and multiply by 100. Going from 80 to 100 gives (100 − 80) ÷ 80 × 100 = 25% increase; going from 100 to 80 gives (80 − 100) ÷ 100 × 100 = 20% decrease. The two are different because the baseline changes.
Percentage change is directional and divides by the starting value, so it needs a clear before and after. Percentage difference is symmetric and divides by the average of the two values, giving the same answer whichever order you write them: 80 and 100 differ by 20 ÷ 90 × 100 = 22.22%. Use change for growth over time and difference for two independent measurements.
Because each percentage is measured against a different base. Cutting 100 by 20% leaves 80, and to get from 80 back to 100 you need to add 20, which is 20 ÷ 80 = 25% of the new, smaller base. The general rule for reversing a change of p percent is 100p ÷ (100 − p) percent in the opposite direction.
Percentage points measure the arithmetic gap between two percentages, while percent measures the relative change between them. An interest rate moving from 45% to 60% has risen 15 percentage points and 33.33% relatively. Saying it rose 15% would be wrong, and the ambiguity is why financial and statistical writing always specifies percentage points, often abbreviated to pp or bps for basis points where one basis point is 0.01 percentage points.
Add the Percentage Change and Difference Calculatorwidget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/percentage-change-difference-calculator"
title="Percentage Change and Difference Calculator — free AltFTool widget"
width="100%" height="640" style="border:0;border-radius:12px;overflow:hidden"
loading="lazy" referrerpolicy="no-referrer-when-downgrade"></iframe>
<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/tools/all/percentage-change-difference-calculator?utm_source=embed&utm_medium=widget">AltFTool — free online tools</a></p>