What's the formula for percent change?

((new − old) / |old|) × 100. A positive result is an increase; negative is a decrease.

Why does 50% off then 20% off not equal 70% off?

Percentages compound. 50% off makes the price 0.50×. Then 20% off makes it 0.50 × 0.80 = 0.40× — that's 60% off, not 70%.

How do I reverse a percent?

If a value already includes 20% VAT, divide by 1.20 to get the pre-tax figure. The calculator does this automatically in "remove tax" mode.

Percentage Calculator — Free Online Tool

Percentage (%)

Of value

20% of 150

What is the Percentage Calculator?

The Percentage Calculator is a free online calculator tools from Markvibe. Calculate percentages, increases, decreases. It runs entirely in your browser — your data never gets uploaded — and works on desktop, tablet and mobile with no sign-up.

Reviewed by The Markvibe Team · Last updated 2026-06-28

Example

A worked example so you know exactly what to expect.

Input

(your input goes here)

Output

(the Percentage Calculator runs in your browser and shows the result instantly)

How to use Percentage Calculator

1Pick the mode: "% of a number" (15% of 240), "X is what % of Y" (45 is what % of 180), or "% change" (from 80 to 100).
2Enter the two numbers — the result, plus a step-by-step worked explanation, appears instantly.
3Switch to the discount tab to compute sale prices (original − %) and the tax tab to add VAT/GST/sales tax.
4Use the tip calculator to split a bill including custom tip %.
5Copy the result or share a link that pre-fills your inputs.