Percentage Calculator — Free Online % Calculator
What is a Percentage Calculator?
A percentage calculator handles the 5 most common percentage problems instantly — finding X% of a number, calculating what % one number is of another, computing percentage change, increasing/decreasing by a percentage, and reverse percentage. No formula memorisation needed.
Percentage Formulas
| Question | Formula | Example |
|---|---|---|
| What is 15% of 200? | (15 ÷ 100) × 200 | = 30 |
| 30 is what % of 200? | (30 ÷ 200) × 100 | = 15% |
| % change from 80 to 100 | ((100−80) ÷ 80) × 100 | = +25% |
| 500 increased by 20% | 500 × (1 + 20/100) | = 600 |
| 30 is 15% of what? | 30 ÷ (15 ÷ 100) | = 200 |
Common Uses of Percentage Calculations
- Discounts & shopping: 30% off ₹2,000 = ₹2,000 × 0.70 = ₹1,400
- Tax calculations: 18% GST on ₹1,000 = ₹1,180 total
- Exam marks: 425/500 = 85% score
- Salary hikes: ₹50,000 + 10% hike = ₹55,000
- Investment returns: ₹1L grew to ₹1.25L = 25% gain
- Tip calculation: 15% tip on $60 bill = $9
Note: Percentage increase and decrease are not symmetric. Increasing by 50% then decreasing by 50% gives you 75% of the original value, not 100%. Always calculate on the correct base value.
Frequently Asked Questions
How do you calculate a percentage of a number?
To find X% of Y: multiply Y by X and divide by 100. Formula: Result = (X ÷ 100) × Y. Examples: 15% of 200 = (15/100) × 200 = 30. 25% of 80 = (25/100) × 80 = 20. 7.5% of 1000 = (7.5/100) × 1000 = 75. Quick shortcut: To find 10%, move decimal point one place left (10% of 350 = 35). To find 5%, halve the 10% answer (5% of 350 = 17.5). To find 1%, move decimal two places left (1% of 350 = 3.5).
How do you calculate what percentage one number is of another?
To find what percentage A is of B: divide A by B and multiply by 100. Formula: Percentage = (A ÷ B) × 100. Examples: 30 is what % of 200? = (30/200) × 100 = 15%. 45 is what % of 180? = (45/180) × 100 = 25%. 7 is what % of 28? = (7/28) × 100 = 25%. Real-world use: Your test score is 72/90 — what %? = (72/90) × 100 = 80%. You spent ₹3,500 out of ₹15,000 budget — what %? = (3500/15000) × 100 = 23.3%.
How do you calculate percentage change?
Percentage change formula: % Change = ((New Value − Old Value) ÷ Old Value) × 100. If positive = increase. If negative = decrease. Examples: Price increases from ₹80 to ₹100: ((100−80)/80) × 100 = +25% increase. Salary drops from $60,000 to $54,000: ((54000−60000)/60000) × 100 = −10% decrease. Stock price moves from $150 to $180: ((180−150)/150) × 100 = +20% gain. Important: % increase and % decrease are NOT symmetrical. A 50% increase followed by a 50% decrease returns you to 75% of the original (not 100%).
How do you add or subtract a percentage from a number?
To increase a number by X%: New Value = Original × (1 + X/100). To decrease a number by X%: New Value = Original × (1 − X/100). Examples: Increase 500 by 20%: 500 × 1.20 = 600. Decrease 500 by 20%: 500 × 0.80 = 400. Price of ₹1,200 with 18% GST added: 1,200 × 1.18 = ₹1,416. Salary of $50,000 with 8% hike: 50,000 × 1.08 = $54,000. Discount: Product costs ₹2,000 with 15% off: 2,000 × 0.85 = ₹1,700.
What is reverse percentage?
Reverse percentage finds the original number when you know what percentage it represents. Formula: Original = Known Value ÷ (Percentage / 100). Examples: 30 is 15% of what number? Original = 30 ÷ 0.15 = 200. A shirt costs ₹850 after a 15% discount — what was the original price? Original = 850 ÷ 0.85 = ₹1,000. VAT-inclusive price is ₹1,180 at 18% VAT — what is the pre-tax price? Pre-tax = 1,180 ÷ 1.18 = ₹1,000. Common use: Working backwards from discounted or tax-inclusive prices.
What is the percentage difference formula?
Percentage difference measures the difference between two values relative to their average. Formula: % Difference = |V1 − V2| / ((V1 + V2) / 2) × 100. Example: Comparing 80 and 100: |80−100| / ((80+100)/2) × 100 = 20/90 × 100 = 22.2%. Note: Percentage difference is different from percentage change. Percentage change has a clear 'before' and 'after'. Percentage difference is used when comparing two equal-status values (e.g., two different prices). Use percentage change for before/after comparisons, percentage difference for comparing two alternatives.
How do you calculate percentage marks?
Percentage of marks = (Marks Obtained / Total Marks) × 100. Examples: You scored 425 out of 500: (425/500) × 100 = 85%. CBSE result: 456/500 = 91.2%. JEE score: 240/300 = 80%. To find marks needed for a target %: Marks needed = (Target % × Total Marks) / 100. To score 90% in a 500-mark exam: (90 × 500) / 100 = 450 marks needed. CGPA to percentage (approximate): CGPA × 9.5 = percentage (used by many Indian universities).
How do you calculate percentage profit or loss?
Percentage profit = ((Selling Price − Cost Price) / Cost Price) × 100. Percentage loss = ((Cost Price − Selling Price) / Cost Price) × 100. Examples: Bought for ₹500, sold for ₹600: Profit = (100/500) × 100 = 20% profit. Bought for ₹1,000, sold for ₹850: Loss = (150/1000) × 100 = 15% loss. Stock bought at $50, sold at $75: Profit = (25/50) × 100 = 50% gain. Property bought for ₹50L, sold for ₹70L: Profit = (20L/50L) × 100 = 40% gain.
How do you calculate tip percentage?
Tip amount = Bill Amount × (Tip % / 100). Total with tip = Bill Amount × (1 + Tip % / 100). Common tip percentages: 10% tip on $45 bill: $45 × 0.10 = $4.50 tip → $49.50 total. 15% tip on $60 bill: $60 × 0.15 = $9.00 tip → $69 total. 20% tip on $80 bill: $80 × 0.20 = $16 tip → $96 total. Quick mental math for 20% tip: Double the bill and move decimal left one place. $75 bill → double = $150 → 20% tip = $15. Use our percentage calculator above with the 'Increase by %' mode for any tip calculation.
How do you calculate percentage increase in salary?
Salary increase % = ((New Salary − Old Salary) / Old Salary) × 100. New salary after % increase = Old Salary × (1 + % / 100). Examples: Salary increases from ₹50,000 to ₹57,500: ((57,500 − 50,000) / 50,000) × 100 = 15% hike. What will ₹80,000 salary be after 12% hike? 80,000 × 1.12 = ₹89,600. After 3 years of 10% annual hikes from ₹60,000: Year 1: 66,000, Year 2: 72,600, Year 3: ₹79,860. Compound effect: Multiple percentage increases compound — a 10% hike each year for 3 years is NOT 30% total, it's 33.1%.
What is the percentage formula for GST calculation?
GST amount = Original Price × GST Rate / 100. Price with GST = Original Price × (1 + GST Rate / 100). To find original price from GST-inclusive price: Original = Inclusive Price / (1 + GST Rate / 100). Examples (18% GST): Product costs ₹1,000 → GST = ₹180 → Total = ₹1,180. Product costs ₹2,500 + 18% GST: 2,500 × 1.18 = ₹2,950. Bill shows ₹1,416 inclusive of 18% GST → Original = 1,416 / 1.18 = ₹1,200. Use our GST Calculator for split CGST/SGST/IGST breakdown.