FreeKit is a collection of free online tools for developers, SEO professionals, designers, students, content creators, and everyday users.

Are all tools completely free?

Yes. Every tool on FreeKit is free to use without subscriptions or hidden charges.

Do I need to create an account?

No. You can use all tools instantly without creating an account.

No. Most tools process data locally in your browser, and we do not permanently store your inputs.

Can I use FreeKit on mobile devices?

Yes. Every tool is fully responsive and works on smartphones, tablets, laptops, and desktop computers.

How often are new tools added?

We regularly add new tools and improve existing ones based on user feedback and industry needs.

Which browsers are supported?

FreeKit supports all modern browsers, including Chrome, Edge, Firefox, Safari, and other Chromium-based browsers.

Can I share these tools with others?

Absolutely. You are welcome to share FreeKit with friends, colleagues, students, and your team.

How do I calculate a percentage of a number?

To find a percentage of a number, multiply the number by the percentage and divide by 100. For example, 15% of 200 = (15 / 100) × 200 = 30. Our calculator does this instantly — just enter the percentage and the number, and the result appears in real time.

What is the difference between percentage increase and percentage decrease?

Percentage increase measures how much a value has grown relative to the original value, using the formula ((New Value - Original Value) / Original Value) × 100. Percentage decrease measures how much a value has dropped, using the same formula but the result is negative. For instance, a price going from $80 to $100 is a 25% increase, while going from $100 to $80 is a 20% decrease.

How do I calculate what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, if you scored 45 out of 60 on a test, the percentage is (45 / 60) × 100 = 75%. Use the "X is what % of Y" tab in our calculator for instant results.

What is percentage difference and how is it different from percentage change?

Percentage difference measures the relative difference between two numbers without implying direction (which is larger). It uses the formula |A - B| / ((A + B) / 2) × 100, dividing by the average of the two values. Percentage change, on the other hand, measures the change from an original value to a new value and always has a direction (increase or decrease), dividing by the original value.

How do I calculate a price after a discount or markup?

For a discount (decrease), multiply the original price by (1 - discount%/100). For a markup (increase), multiply by (1 + increase%/100). For example, a $50 item with a 20% discount costs $50 × 0.80 = $40. Our "X decreased/increased by Y%" tabs handle this automatically.

Can I use this calculator for tips and gratuity?

Yes! To calculate a tip, use the "What is X% of Y?" tab. Enter the tip percentage (e.g., 18%) as X and the bill amount as Y. For example, 18% of $85 = $15.30. You can also use our dedicated Tip Calculator for a more detailed bill-splitting experience.

Why do percentage increase and decrease from the same values differ?

This is a common source of confusion. A 50% increase followed by a 50% decrease does not return you to the original value. For example, $100 increased by 50% = $150, then $150 decreased by 50% = $75. This happens because the percentage is applied to a different base value each time — the increase is based on $100, but the decrease is based on $150.

How accurate is this percentage calculator?

This calculator uses JavaScript's built-in floating-point arithmetic and provides results with up to 10 decimal places for precision. For most everyday uses (finance, shopping, grades), this level of precision is more than sufficient. Results are formatted to a reasonable number of decimal places for readability, with the option to see full precision.

Is my data stored or sent to a server?

No. This percentage calculator runs entirely in your browser using client-side JavaScript. None of the numbers you enter are sent to any server, stored in any database, or shared with any third party. As soon as you close or refresh the page, all entered data is gone.

What are some real-world uses for percentage calculations?

Percentages are used everywhere: calculating sales tax and discounts while shopping, determining tip amounts at restaurants, analyzing investment returns and stock price changes, figuring out grade averages in school, measuring body fat changes, comparing price differences between stores, and calculating salary raises or inflation rates. Our calculator covers all these scenarios with its five calculation modes.

Percentage Calculator

Calculate percentages, increases, decreases, and differences.

BeginnerCalculatorsFreev1.0.0Updated Jun 15, 2025

Percentage Calculator

Choose a calculation mode below — results update in real time

Percentage (X)

Number (Y)

Example: What is 15% of 200? Answer: 30

Quick examples

100% Private — Runs in Your Browser

All percentage calculations happen locally using JavaScript. Your numbers are never sent to any server, stored, or shared. Close the tab and your data is gone.

How to Use the Percentage Calculator

Our percentage calculator offers five calculation modes. Here is how to get started:

Select a calculation mode — Choose from the five tabs: X% of Y, What %, Change, Increase, or Decrease.
Enter your numbers — Type your values into the input fields. Results appear instantly as you type.
Review the formula — Every result shows the step-by-step formula used so you can verify the math.
Try quick examples — Click any pre-built example button to instantly populate the fields with common calculations.

Features

Five calculation modes covering all common percentage scenarios
Real-time results — no submit button needed, updates as you type
Step-by-step formula display for every calculation
Quick example buttons for instant demo of each mode
Increase/decrease detection with color-coded results
Support for decimal percentages (e.g., 8.5%, 0.25%)
Responsive design that works on mobile, tablet, and desktop
100% browser-based — no server, no data collection
Clean, accessible interface with proper ARIA labels
Formatted number output with locale-aware thousands separators

Percentage Formulas Explained

Percentage of a Number

Result = (X / 100) × Y

Multiply the percentage (as a decimal) by the base number. Example: 15% of 200 = 0.15 × 200 = 30.

What Percent?

% = (Part / Whole) × 100

Divide the part by the whole and multiply by 100. Example: 30 is (30 / 200) × 100 = 15% of 200.

Percentage Change

% = ((New − Old) / Old) × 100

Subtract the original from the new value, divide by the original, and multiply by 100. Positive = increase, negative = decrease.

Percentage Increase

Result = X × (1 + Y / 100)

Add the percentage amount to the original. Example: 80 increased by 25% = 80 × 1.25 = 100.

Percentage Decrease

Result = X × (1 − Y / 100)

Subtract the percentage amount from the original. Example: 120 decreased by 20% = 120 × 0.80 = 96.

Percentage Difference

% = |A − B| / ((A + B) / 2) × 100

Measures the absolute difference relative to the average of two values, with no direction implied.

Common Use Cases

Shopping Discounts

Calculate the final price after a sale. Use the Decrease tab: enter the original price and discount percentage.

Tip Calculation

Find how much to tip at a restaurant. Use the X% of Y tab: enter tip % and bill amount. Or try our dedicated Tip Calculator.

Investment Returns

Measure stock or portfolio growth. Use the Percentage Change tab to see gain or loss over time.

Grade Averages

Convert a raw score to a percentage. Use the What % tab: enter your score and the total possible points.

Salary Raises

Calculate your new salary after a raise. Use the Increase tab: enter current salary and raise percentage.

Tax Calculations

Find the tax amount on a purchase. Use the X% of Y tab: enter the tax rate and pre-tax price.

Inflation Impact

See how prices change over time. Use the Percentage Change tab with old and new prices.

Markup Pricing

Set selling prices based on cost. Use the Increase tab: enter your cost and desired markup percentage.

Tips for Percentage Calculations

Remember that percentage increase and decrease are not symmetric: 50% up from 100 is 150, but 50% down from 150 is 75, not 100.
For quick mental math, 10% of any number is simply the number with the decimal shifted one place left.
To find 5%, calculate 10% and then halve it. To find 15%, calculate 10% and add half of 10%.
When comparing two percentages, always check what base value they refer to — percentages of different totals cannot be directly compared.
Need to convert between units? Use our Unit Converter for length, weight, temperature, and more.
Calculating a restaurant bill split? Our Tip Calculator handles tips, splits, and total — all in one tool.
Checking your health metrics? Our BMI Calculator works great alongside percentage-based body fat tracking.
Planning a shopping trip? Our Discount Calculator gives you the final price after multiple discounts and tax.
A percentage greater than 100% simply means the part is larger than the whole — this is common in growth metrics.
All calculations use your browser's JavaScript engine. No data is ever sent to a server.

Percentage in Everyday Life

Finance and Banking

Interest rates, loan APRs, investment returns, and inflation are all expressed as percentages. Understanding percentage change helps you evaluate whether your savings are keeping pace with inflation or whether an investment is truly growing.

Shopping and Sales

Retailers use percentages for discounts (e.g., “30% off”), sales tax, and coupon savings. Being able to quickly calculate percentage decreases lets you compare deals and find the best price across different stores.

Health and Nutrition

Daily value percentages on nutrition labels show how a food fits into your diet. Body fat percentage, BMI percentiles, and blood oxygen levels are all critical health metrics expressed as percentages.

Education and Grades

Test scores, class averages, grade curves, and passing thresholds are all percentage-based. Knowing how to calculate what percentage a raw score represents helps students and parents track academic progress.

Frequently Asked Questions

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How to Use the Percentage Calculator

Our percentage calculator offers five calculation modes. Here is how to get started:

Select a calculation mode — Choose from the five tabs: X% of Y, What %, Change, Increase, or Decrease.

Enter your numbers — Type your values into the input fields. Results appear instantly as you type.

Review the formula — Every result shows the step-by-step formula used so you can verify the math.

Try quick examples — Click any pre-built example button to instantly populate the fields with common calculations.

Features

Five calculation modes covering all common percentage scenarios

Real-time results — no submit button needed, updates as you type

Step-by-step formula display for every calculation

Quick example buttons for instant demo of each mode

Increase/decrease detection with color-coded results

Support for decimal percentages (e.g., 8.5%, 0.25%)

Responsive design that works on mobile, tablet, and desktop

100% browser-based — no server, no data collection

Clean, accessible interface with proper ARIA labels

Formatted number output with locale-aware thousands separators

Percentage Formulas Explained

Percentage of a Number

Result = (X / 100) × Y

Multiply the percentage (as a decimal) by the base number. Example: 15% of 200 = 0.15 × 200 = 30.

What Percent?

% = (Part / Whole) × 100

Divide the part by the whole and multiply by 100. Example: 30 is (30 / 200) × 100 = 15% of 200.

Percentage Change

% = ((New − Old) / Old) × 100

Subtract the original from the new value, divide by the original, and multiply by 100. Positive = increase, negative = decrease.

Percentage Increase

Result = X × (1 + Y / 100)

Add the percentage amount to the original. Example: 80 increased by 25% = 80 × 1.25 = 100.

Percentage Decrease

Result = X × (1 − Y / 100)

Subtract the percentage amount from the original. Example: 120 decreased by 20% = 120 × 0.80 = 96.

Percentage Difference

% = |A − B| / ((A + B) / 2) × 100

Measures the absolute difference relative to the average of two values, with no direction implied.

Common Use Cases

Shopping Discounts

Calculate the final price after a sale. Use the Decrease tab: enter the original price and discount percentage.

Tip Calculation

Find how much to tip at a restaurant. Use the X% of Y tab: enter tip % and bill amount. Or try our dedicated Tip Calculator.

Investment Returns

Measure stock or portfolio growth. Use the Percentage Change tab to see gain or loss over time.

Grade Averages

Convert a raw score to a percentage. Use the What % tab: enter your score and the total possible points.

Salary Raises

Calculate your new salary after a raise. Use the Increase tab: enter current salary and raise percentage.

Tax Calculations

Find the tax amount on a purchase. Use the X% of Y tab: enter the tax rate and pre-tax price.

Inflation Impact

See how prices change over time. Use the Percentage Change tab with old and new prices.

Markup Pricing

Set selling prices based on cost. Use the Increase tab: enter your cost and desired markup percentage.

Tips for Percentage Calculations

Remember that percentage increase and decrease are not symmetric: 50% up from 100 is 150, but 50% down from 150 is 75, not 100.

For quick mental math, 10% of any number is simply the number with the decimal shifted one place left.

To find 5%, calculate 10% and then halve it. To find 15%, calculate 10% and add half of 10%.

When comparing two percentages, always check what base value they refer to — percentages of different totals cannot be directly compared.

Need to convert between units? Use our Unit Converter for length, weight, temperature, and more.

Calculating a restaurant bill split? Our Tip Calculator handles tips, splits, and total — all in one tool.

Checking your health metrics? Our BMI Calculator works great alongside percentage-based body fat tracking.

Planning a shopping trip? Our Discount Calculator gives you the final price after multiple discounts and tax.

A percentage greater than 100% simply means the part is larger than the whole — this is common in growth metrics.

All calculations use your browser's JavaScript engine. No data is ever sent to a server.