Percentage Calculator

Intro

This calculator covers the most common percentage questions in one place: percent of a number, what percent one number is of another, percentage increase or decrease, and adding or subtracting a percentage from a starting value. It is useful for discounts, margins, markups, budgeting, classroom math, and quick business checks.

1. What is X% of Y?

Percent

Number

2. X is what percent of Y?

Part

Whole

3. Percentage change

From

4. Add or subtract a percentage

Starting value

Percent

How it works

The page uses standard percentage formulas directly in the browser.

percent of number = rate / 100 x base
what percent = part / whole x 100
percentage change = (new - old) / old x 100
adjusted value = base x (1 +/- rate / 100)

Limitations: this tool does not decide whether your business context should use margin, markup, percentage-point change, or absolute change. It gives the math; you still need the right commercial or reporting interpretation.

Practical use scenarios

Check discounts and markups during shopping or procurement.
Measure salary changes, price increases, or KPI movement.
Convert ratios into percentages for reporting or schoolwork.
Quickly test what happens when a number goes up or down by a chosen percentage.

Related tools

VAT Calculator Loan Payment Calculator Inflation Calculator Unit Converter

FAQ

What is the difference between percentage change and percentage points?

Percentage change compares relative growth or decline, while percentage points describe the direct difference between two percentage values.

Can I use this for discounts and markups?

Yes. The add/subtract section is useful for rough discount and markup checks.

Why does percent change fail when the starting value is zero?

Because the formula divides by the starting value, and division by zero is undefined.

Does the tool store my numbers?

No. The calculation runs in your browser.