Four calculation modes in one tool: find a percentage of a number, compare two values as a percentage, calculate percentage change between two values, or use the built-in GST calculator for Indian tax rates.
30
15% of 200 = 30
15%
30 is 15% of 200
25% increase
From 80 to 100 is a 25% increase
Base price
₹1,000
GST (18%)
+₹180
Total
₹1,180
How to use this percentage calculator
X% of Y: Find what a percentage of a number equals. E.g., "15% of 200 = 30."
X is ?% of Y: Find what percentage one number is of another. E.g., "30 out of 200 = 15%."
% Change: Calculate percentage increase or decrease between two values.
GST Calculator: Add GST to a base price or extract base price from a GST-inclusive total. Select a GST slab or enter a custom rate.
Percentage formulas
Mode 1 — X% of Y: Result = (X ÷ 100) × Y
Mode 2 — X is ?% of Y: Result = (X ÷ Y) × 100
Mode 3 — % change: Result = ((New − Old) ÷ |Old|) × 100
GST add: GST = Base × (Rate ÷ 100) | Total = Base + GST
GST extract: Base = Total ÷ (1 + Rate ÷ 100)
Examples:
Mode 1: 15% of ₹200 → (15 ÷ 100) × 200 = 30
Mode 2: 30 out of 200 → (30 ÷ 200) × 100 = 15%
Mode 3: From 80 to 100 → ((100−80) ÷ 80) × 100 = 25% increase
GST: ₹1,000 + 18% → ₹1,000 × 0.18 = ₹180 → Total ₹1,180
Percentages: a complete guide
What is a percentage?
The word "percent" comes from the Latin "per centum" — literally "by the hundred." A percentage expresses a number as a fraction of 100. Whether you are reading a bank interest rate, calculating a discount, interpreting a news statistic, or working out GST on a bill, percentages are the universal language of comparison and proportion.
Percentage points vs percentages — a critical distinction
If a tax rate increases from 5% to 6%, it has increased by 1 percentage point. But it has also increased by 20% as a rate (1 is 20% of 5). These are not the same statement and confusing them leads to significant errors in financial analysis, journalism, and everyday decision-making. Always clarify which you mean when discussing changes in rates or proportions.
Why 50% up and 50% down does not return to the original value
₹100 increased by 50% becomes ₹150. ₹150 decreased by 50% becomes ₹75 — not ₹100. The second percentage applies to the new, larger base. This asymmetry is fundamental to understanding investment returns, salary negotiations, and discount calculations. A stock that drops 50% needs to rise 100% just to return to its original value.
Calculating the original value before a percentage change
To find the original value from a percentage-changed value: divide by (1 + change/100) for an increase, or (1 - decrease/100) for a decrease. Example: ₹600 is 20% more than the original → original = 600 ÷ 1.20 = ₹500. This is the same principle used to extract base prices from GST-inclusive totals.
Percentage = (Part ÷ Whole) × 100. Every percentage question is a variation of this. The three modes on this calculator — find a percentage, compare two values, and calculate change — are all derived from this single formula.
How do I calculate a discount? ▼
Discount amount = Original price × (Discount% ÷ 100). Sale price = Original price − Discount. Example: 20% off ₹800 → Discount = ₹800 × 0.20 = ₹160 → Sale price = ₹640.
How do I find the original price after a discount? ▼
Original = Sale price ÷ (1 − Discount%/100). Example: you pay ₹640 after a 20% discount → Original = ₹640 ÷ 0.80 = ₹800.
What is the percentage change formula? ▼
% Change = ((New value − Old value) ÷ |Old value|) × 100. A positive result is an increase; negative is a decrease. Example: from ₹80 to ₹100 → ((100−80) ÷ 80) × 100 = 25% increase.
How do I calculate GST on a price? ▼
GST Amount = Base price × (GST rate ÷ 100). Total = Base + GST. To extract base from total: Base = Total ÷ (1 + rate/100). Use the GST Calculator mode on this page for instant results.
What are the 4 GST rates in India? ▼
5% on essential goods (packaged food, certain textiles), 12% on processed food and some electronics, 18% on most services and standard goods, 28% on luxury items and automobiles. Some items are exempt (0% GST).
Why does 50% increase then 50% decrease not return to the original? ▼
Because each percentage applies to the current value, not the original. ₹100 + 50% = ₹150. ₹150 − 50% = ₹75. The second percentage acts on the higher base of ₹150, so the decrease is larger than the original increase in absolute terms.
How do I calculate markup vs margin? ▼
Markup = (Profit ÷ Cost) × 100. Margin = (Profit ÷ Selling price) × 100. Example: Cost ₹100, sell for ₹125. Profit = ₹25. Markup = 25%; Margin = 20%. These are two ways of expressing the same profit but they give different numbers.