Percentage Calculator
Instantly calculate percentages, percentage change, increase, decrease, and more — free, accurate, and no login required.
What is [X]% of [Y]?
Calculates the percentage increase or decrease from old to new value.
What percentage is X of Y?
If [X]% of original = [Result], find the original number.
How to Use the Percentage Calculator
- 1Choose Calculation Type: Select one of four modes — X% of Y, Percentage Change, What % is X of Y, or Find Original Number — using the tabs at the top.
- 2Enter Your Values: Fill in the required number fields displayed for your selected mode. All inputs accept decimals.
- 3Press Calculate: Click the Calculate button or press Enter to compute the result instantly in your browser.
- 4Review the Result: The answer appears below with the formula used and a plain-English explanation of the calculation.
- 5Clear and Recalculate: Hit Clear to reset all inputs and try a different calculation with fresh values.
Key Features
⚡ Four Calculation Modes
Handles percentages of a number, percentage change, part-to-whole ratio, and reverse percentage — all in one place.
🔒 100% Private
All calculations happen in your browser. No data is sent to any server, so your numbers stay completely private.
📱 Mobile-Friendly
Works perfectly on smartphones, tablets, and desktops with a responsive layout and large tap targets for easy use.
✅ Instant Validation
Inline error messages guide you immediately if a field is empty or invalid, so you always get a correct result.
📋 Formula Displayed
Every result includes the formula used and a plain-language breakdown so you understand exactly how the answer was reached.
🔁 Decimal Support
Enter whole numbers or decimals in any field. The calculator handles fractional percentages and values accurately.
Formula & How It Works
Mode 1: X% of Y
Result = (Percentage / 100) × NumberDivide the percentage by 100 to convert it to a decimal, then multiply by the number. Example: 15% of 800 = (15/100) × 800 = 120.
Mode 2: Percentage Change
% Change = ((New − Old) / |Old|) × 100Subtract the old value from the new value, divide by the absolute old value, then multiply by 100. A positive result is an increase; negative is a decrease.
Mode 3: What % is X of Y?
Percentage = (X / Y) × 100Divide the part (X) by the whole (Y), then multiply by 100 to get the percentage. Example: 45 of 180 = (45/180) × 100 = 25%.
Mode 4: Find Original Number
Original = Result × (100 / Percentage)Multiply the known result by (100 ÷ percentage applied). Example: If 20% of original = 60, then original = 60 × (100/20) = 300.
Practical Examples
🇮🇳 Example 1 — GST Calculation (India)
A shopkeeper in Mumbai sells a product worth ₹2,000 and needs to add 18% GST. Using Mode 1: 18% of 2000 = (18/100) × 2000 = ₹360. Total invoice amount = ₹2,360.
🇮🇳 Example 2 — Exam Marks (India)
A student in Delhi scored 378 out of 500 in their Class 12 board exam. Using Mode 3: (378/500) × 100 = 75.6%. This is the percentage score to report on college applications.
🌍 Example 3 — Sales Growth (International)
A UK-based online store had revenue of £12,000 in January and £15,600 in February. Using Mode 2: ((15600 − 12000) / 12000) × 100 = 30% increase in monthly revenue.
🇮🇳 Example 4 — Discount Reverse Calculation (India)
A product after a 25% discount is selling for ₹750. What was the original price? Using Mode 4: 750 × (100/25) = ₹3,000. Wait — the discount amount is 25%, so ₹750 is 75% of original. Original = 750 × (100/75) = ₹1,000.
What Is a Percentage Calculator?
A percentage calculator is a digital tool that automates the most common percentage-based computations. Percentages appear in nearly every area of daily life — tax rates, discount offers, exam scores, profit margins, interest rates, and statistical data. Manual calculation can introduce errors, especially with decimal values or multi-step problems.
This tool covers four essential percentage calculation types in a single interface. Whether you are a student checking exam scores, a business owner applying GST, or a consumer evaluating a discount, this calculator delivers instant, accurate results without any apps or logins. It runs entirely in your browser, so your inputs are never stored or transmitted.
By showing the formula alongside every result, the tool also helps you learn and verify the math — making it useful for education as well as practical tasks.
Want to learn more about percentage formulas, common use cases, and tips for using percentages in business and study?
Read Full Guide →Frequently Asked Questions
Yes, this Percentage Calculator is completely free to use. No login, signup, or payment is required. You can use it unlimited times.
You can calculate: (1) X% of a number, (2) What percentage X is of Y, (3) Percentage increase or decrease between two numbers, and (4) The original number when a percentage result is known.
The basic percentage formula is: Percentage = (Part / Whole) × 100. For example, to find 20% of 500, compute (20/100) × 500 = 100.
Percentage Change = ((New Value − Old Value) / Old Value) × 100. A positive result means an increase; a negative result means a decrease.
Yes. The Percentage Calculator is fully mobile-responsive and works on all smartphones, tablets, and desktop browsers without any app download.
No. All calculations are done locally in your browser. No data is sent to any server, ensuring complete privacy.
Use the "X is what % of Y?" mode. Enter both numbers and the calculator computes (X / Y) × 100 to give you the percentage instantly.
Yes. Use the "Find Original Number" mode. Enter the known result and the percentage applied, and the tool computes: Original = Value × (100 / Percentage).
Percentage increase means a value has grown relative to the original. Percentage decrease means it has shrunk. Both use the same formula — the sign of the result tells you which it is.
Yes. The calculator uses standard mathematical formulas and returns results rounded to two decimal places, making it suitable for financial estimates and exam preparation.
Once the page is loaded, all calculations run locally in your browser. However, an active internet connection is needed to initially load the page.
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