Percentage Calculator

Calculate percentages, percentage change and percentage of a number.

Last updated: 14 August 2026

Processed locally — your files are not uploaded to any server.

Comprehensive Guide & Specifications

Everything you need to know about using Percentage Calculator effectively.

What is Percentage Calculator and Why Use It?

Three questions cover almost every percentage problem that comes up in ordinary work: what is X percent of a number, what percentage is one number of another, and what is the change between two values. This handles all three, so you pick the question rather than remembering which way the division goes. It suits checking a bill, sizing a change in a metric, or converting a fraction into the percentage a report expects. Three facts about percentages catch people out and are worth carrying away. A rise followed by an equal fall does not return you to the start — 100 up ten percent is 110, and 110 down ten percent is 99. Percentage change is always measured against the starting value, so swapping which figure is the 'from' changes the answer. And a rate moving from 5% to 7% is up two percentage points, or up 40%.

Step-by-Step Instructions

1
Choose your calculation mode (percentage of a number, percentage increase, or ratio).
2
Enter your initial value and secondary number into the respective fields.
3
View instant results alongside the underlying mathematical step breakdown.

Formula / Calculations Explained

Percentage and Percentage Difference Formulas

% Change = ((New Value - Old Value) / Old Value) × 100

Solves foundational percentage math: determining fractions of a whole, calculating percentage increase/decrease, and comparing proportional changes.

Important Considerations

A percentage rise then an equal percentage fall does not return you to the start: 100 up 10% is 110, and 110 down 10% is 99.
Percentage change is always measured against the starting value, so swapping which number is 'from' changes the answer.
Percentage points and percentages differ — a rate moving from 5% to 7% is up two percentage points, or up 40%.

Frequently Asked Questions

How do you calculate percentage increase between two numbers?▼

Subtract the original value from the new value, divide the difference by the original value, and multiply by 100.

Can this calculator handle negative percentage changes?▼

Yes, if the new value is less than the original value, the calculator displays a negative percentage indicating a percentage decrease.

Is this percentage calculator free to use?▼

Yes, it is 100% free, runs instantly in your web browser, and requires no account or download.

Worked example

Example only — not financial advice

This calculator supports two primary percentage calculations. For the first option ("What is X% of Y?"), the formula is (X ÷ 100) × Y. In our example, calculating 15% of 200 yields 30.00. For the second option ("X is what % of Y?"), the formula is (X ÷ Y) × 100. In our example, determining what percentage 50 is of 250 yields 20.00%.

Worked example: Calculating percentages and portions
Example input	Value
Scenario 1: Percentage rate	15%
Scenario 1: Base value	200
Scenario 2: Part value	50
Scenario 2: Whole value	250
Scenario 1: 15% of 200	30.00
Scenario 2: 50 is what % of 250	20.00%

These figures illustrate how the Percentage Calculator computes its result for the example inputs above — they are not a rate offer, a market quote, or a recommendation for your own numbers. Enter your own figures in the calculator above to get a result that applies to you.

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