A percentage calculator instantly solves any percentage problem — from discounts and GST to exam scores and profit margins. Percentages are everywhere — from a 20% discount at your favourite store to an 8.5% interest rate on a home loan, from your exam score to the GST on your restaurant bill. Yet many people still reach for a calculator and wonder if they are applying the right formula.
This guide demystifies every type of percentage calculation with clear formulas, worked examples, and a quick-reference table covering the 20 most commonly searched calculations. By the end, you will be able to solve any percentage problem in seconds — and understand exactly what you calculated.
Calculate Any Percentage Instantly — Free
Solve all three types of percentage problems: find X% of Y, find what % one number is of another, or calculate percentage change. Includes GST and discount modes.
What Is a Percentage? Definition and Everyday Examples
A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin per centum — "per hundred." A percentage of 25% means 25 out of every 100, or 0.25 as a decimal, or 1/4 as a fraction.
Where percentages appear in daily life
- Shopping — "30% off sale," "Buy 2 get 1 free" (effectively 33.3% off)
- Finance — "8.5% annual interest," "18% GST," "15% TDS"
- Health — "Body fat percentage," "Blood oxygen 98%," "BMI percentile"
- Statistics — "Voter turnout 62%," "Market share 45%," "Growth rate 12% YoY"
- Academics — "Scored 87 out of 100 = 87%"
Percentage vs percentage points
This is one of the most common sources of confusion. If your savings account interest rate rises from 4% to 6%, it increased by 2 percentage points — but by 50% (because 2 is 50% of 4). These are completely different statements. Percentage points measure the absolute arithmetic difference; percentage change measures the relative change.
"Interest rates increased by 2%" can mean either a 2 percentage point increase (4% → 6%) or a 2% relative increase (4% → 4.08%). Always clarify which is meant in financial and statistical contexts.
The Three Core Percentage Formulas (With Worked Examples)
All percentage calculations reduce to three fundamental question types. Master these and you can solve any percentage problem.
Formula 1: What is X% of Y?
Result = (X ÷ 100) × YExample: What is 15% of ₹2,000?
= (15 ÷ 100) × 2,000 = 0.15 × 2,000 = ₹300
Use case: Calculating a tip, a discount amount, a GST component, or a commission.
Formula 2: X is what percentage of Y?
Percentage = (X ÷ Y) × 100Example: You scored 68 out of 80 in an exam. What percentage is that?
= (68 ÷ 80) × 100 = 0.85 × 100 = 85%
Use case: Converting a score to a percentage, calculating market share, finding what proportion one number is of another.
Formula 3: Percentage change from X to Y
% Change = ((New Value − Old Value) ÷ Old Value) × 100Example: A product's price changed from ₹800 to ₹960. What is the percentage increase?
= ((960 − 800) ÷ 800) × 100 = (160 ÷ 800) × 100 = 20% increase
Use case: Price changes, salary hikes, population growth, revenue comparisons.
To find 10% of any number, simply move the decimal point one place to the left. 10% of ₹4,500 = ₹450. Then 5% is half that (₹225), 20% is double (₹900), 15% is ₹450 + ₹225 = ₹675. Mental arithmetic becomes fast with this approach.
Quick Reference: 25 Most-Searched Percentage Calculations
These are the most commonly searched percentage calculations on Google. Bookmark this table for instant reference.
| Question | Formula Used | Answer |
|---|---|---|
| What is 10% of 100? | (10÷100)×100 | 10 |
| What is 20% of 500? | (20÷100)×500 | 100 |
| What is 15% of 200? | (15÷100)×200 | 30 |
| What is 5% of 1000? | (5÷100)×1000 | 50 |
| What is 25% of 80? | (25÷100)×80 | 20 |
| What is 18% of 500? (GST) | (18÷100)×500 | 90 |
| 30 is what % of 150? | (30÷150)×100 | 20% |
| 45 is what % of 180? | (45÷180)×100 | 25% |
| 60 is what % of 400? | (60÷400)×100 | 15% |
| % change: 500 → 600 | ((600−500)÷500)×100 | 20% increase |
| % change: 800 → 680 | ((680−800)÷800)×100 | 15% decrease |
| % change: 1000 → 1250 | ((1250−1000)÷1000)×100 | 25% increase |
| 20% off ₹1,500 | 1500 − (20÷100)×1500 | ₹1,200 |
| 30% off ₹2,000 | 2000 − (30÷100)×2000 | ₹1,400 |
| Price after 10% increase from ₹900 | 900 × 1.10 | ₹990 |
For non-round numbers like "what is 17.5% of ₹3,847," use ToolsArena's percentage calculator for instant precision. The formula is always (17.5 ÷ 100) × 3,847 = ₹672.23.
Percentage Increase, Decrease and Difference Explained
These three concepts are related but distinct. Confusing them leads to wrong calculations in finance, statistics, and everyday math.
Percentage increase
% Increase = ((New − Old) ÷ Old) × 100Used when a value grows: salary hike from ₹40,000 to ₹46,000 = ((46,000 − 40,000) ÷ 40,000) × 100 = 15% increase
Percentage decrease
% Decrease = ((Old − New) ÷ Old) × 100Used when a value falls: stock price drops from ₹250 to ₹200 = ((250 − 200) ÷ 250) × 100 = 20% decrease
Percentage difference (between two values)
% Difference = (|Value1 − Value2| ÷ ((Value1 + Value2) ÷ 2)) × 100Used when neither value is a "baseline." If two machines produce 480 and 520 units, the percentage difference = (|480−520| ÷ 500) × 100 = 8% difference.
Reverse percentage: finding the original value
If a price after 20% discount is ₹960, what was the original price?
Original = ₹960 ÷ (1 − 0.20) = ₹960 ÷ 0.80 = ₹1,200
If you know the discounted price and the discount %, divide the discounted price by (1 − discount%). If an item costs ₹425 after a 15% discount, the original price = ₹425 ÷ 0.85 = ₹500.
Percentage Calculations for India: GST, Discounts and TDS
For Indian users, these percentage applications come up constantly in everyday financial life.
GST (Goods and Services Tax) calculations
India uses multiple GST slabs: 0%, 5%, 12%, 18%, and 28%. Here is how to calculate each:
| GST Rate | Base Price (₹) | GST Amount | Total Price |
|---|---|---|---|
| 5% | ₹1,000 | ₹50 | ₹1,050 |
| 12% | ₹1,000 | ₹120 | ₹1,120 |
| 18% | ₹1,000 | ₹180 | ₹1,180 |
| 28% | ₹1,000 | ₹280 | ₹1,280 |
To extract GST from a GST-inclusive price:
GST Amount = (Inclusive Price × GST Rate) ÷ (100 + GST Rate)
Example: Extract 18% GST from ₹1,180: (1,180 × 18) ÷ 118 = ₹180 GST, base price = ₹1,000
Discount percentage calculations
Sale season tip: if an item has a "flat 40% off" label and is now priced at ₹1,200:
Original MRP = ₹1,200 ÷ (1 − 0.40) = ₹1,200 ÷ 0.60 = ₹2,000 MRP
TDS (Tax Deducted at Source)
Most professional payments in India have 10% TDS. If your invoice is ₹50,000 and TDS is 10%:
TDS deducted = ₹5,000. Net payment received = ₹45,000. You can claim the ₹5,000 as advance tax credit when filing ITR.
To convert your board exam marks to percentage: (Total Marks Obtained ÷ Maximum Marks) × 100. For CBSE class 12 with 495/500: (495 ÷ 500) × 100 = 99%. For aggregate of 5 subjects with total 450/500: 90%.
How to Use the Tool (Step by Step)
- 1
Open ToolsArena Percentage Calculator
Navigate to the free percentage calculator — no account or download required.
- 2
Select your calculation type
Choose between: (1) X% of Y, (2) X is what % of Y, or (3) Percentage change from X to Y.
- 3
Enter your values
Type in the numbers. The calculator accepts decimals — e.g., 8.5% or ₹12,499.
- 4
See the instant result
Your answer appears immediately with the formula shown so you understand how it was calculated.
- 5
Try reverse percentage
Use the "find original value" mode to reverse-calculate from a discounted or tax-inclusive price.
Frequently Asked Questions
What is the formula to calculate percentage?+−
There are three core formulas: (1) X% of Y = (X÷100)×Y; (2) X is what % of Y = (X÷Y)×100; (3) Percentage change = ((New−Old)÷Old)×100. Most percentage questions fit one of these three patterns.
How do I calculate 20% off a price?+−
Multiply the original price by 0.20 to find the discount amount, then subtract from the original price. Example: 20% off ₹1,500 = ₹1,500 × 0.20 = ₹300 discount → final price = ₹1,200. Shortcut: multiply original price by 0.80 directly.
How do I calculate GST?+−
To add GST to a base price: Final Price = Base Price × (1 + GST%/100). For 18% GST on ₹1,000: ₹1,000 × 1.18 = ₹1,180. To extract GST from a GST-inclusive price: GST Amount = (Price × Rate) ÷ (100 + Rate).
What is the difference between percentage and percentage points?+−
Percentage points measure the arithmetic difference between two percentages. If unemployment falls from 6% to 4%, it fell by 2 percentage points — but by 33.3% (because 2 is 33.3% of 6). The two measures tell very different stories. Percentage points are absolute; percentage change is relative.
How do I calculate percentage increase?+−
Percentage Increase = ((New Value − Old Value) ÷ Old Value) × 100. If a salary increases from ₹40,000 to ₹47,000: ((47,000 − 40,000) ÷ 40,000) × 100 = 17.5% increase.
How do I find the original price after a percentage discount?+−
Divide the discounted price by (1 − discount rate). If a product is ₹720 after a 10% discount: Original = ₹720 ÷ 0.90 = ₹800. If after 25% discount: ₹720 ÷ 0.75 = ₹960.
How do I calculate marks percentage in India?+−
Marks Percentage = (Total Marks Obtained ÷ Maximum Marks) × 100. For CBSE class 10 with 465/500: (465 ÷ 500) × 100 = 93%. For aggregate percentage across 5 subjects each out of 100, with scores 85, 90, 78, 92, 88: (433 ÷ 500) × 100 = 86.6%.
What is 1% of 1 crore?+−
1% of 1 crore (₹1,00,00,000) = ₹1,00,000 (₹1 lakh). Formula: (1 ÷ 100) × 1,00,00,000 = ₹1,00,000. Similarly, 0.1% of 1 crore = ₹10,000, and 10% of 1 crore = ₹10,00,000 (₹10 lakh).
Calculate Any Percentage Instantly — Free
Solve all three types of percentage problems: find X% of Y, find what % one number is of another, or calculate percentage change. Includes GST and discount modes.
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