How to Calculate Percentages: Percent Of, Percent Change and More
"Prices up 18%", "40% off", "marks: 437 out of 500", "the stock fell 12%, then rose 12%, so we're even, right?" (No.) Percentages show up daily, and the reverse ones are where mental maths goes wrong. Percentage calculator answers the common percentage questions with two numbers each.
Steps
- Choose the question.
- Enter the two numbers it asks for.
- Read the result. Switch questions without reloading.
The questions and their formulas
- What is X% of Y? Y × X/100. 18% of ₹2,500 = ₹450.
- X is what percent of Y? X ÷ Y × 100. 437 of 500 = 87.4%.
- Percent change from A to B: (B − A) ÷ A × 100. 80 to 100 is a 25% increase. A fall shows as a negative percent. The starting number can't be zero.
- Increase or decrease X by P%: X × (1 ± P/100). ₹500 plus 18% GST = ₹590.
- X is P% of what? X ÷ (P/100). If ₹450 is 18%, the total is ₹2,500.
Decimals work in all of them.
Three mistakes that catch people
1. Up then down isn't even. A 12% fall followed by a 12% rise leaves you below where you started: 100 → 88 → 98.56. That's because the rise is on a smaller base.
2. Removing GST isn't subtracting 18%. If ₹590 includes 18% GST, the pre-tax price is ₹590 ÷ 1.18 = ₹500, not ₹590 − 18% = ₹483.80. Use "X is P% of what" with P = 118.
3. Percentage points vs percent. An interest rate going from 10% to 12% is a rise of 2 percentage points, but a 20% increase in the rate. News reports mix these up constantly.
Everyday examples
- Discount: a ₹3,999 jacket at 35% off. Decrease by 35% → ₹2,599.35.
- Salary hike: ₹62,000 to ₹68,500 a month is a 10.48% increase.
- Exam marks: 437/500 → 87.4%.
- Tip: 10% of a ₹1,840 bill → ₹184.
- Investment: ₹1,20,000 to ₹1,38,000 → 15% gain.
- Weight loss: 82 kg to 76 kg → −7.3%.
Exam score planning
For "what do I need on the final to get an A", where assessments have different weights, use the dedicated Final grade calculator. It accounts for weights, which a plain percentage can't.
Tips
- Name your base. Every percent is "of" something. Many disagreements are really about which number is the base.
- For repeated growth (interest, inflation over years), percentages compound; use a compound interest approach rather than adding percentages.
- Round at the end, not in the middle, especially with money.
Percent of what? Discounts on discounts
Shops love "extra 20% off sale prices". A ₹2,000 item at 30% off, then an extra 20%, is not 50% off. The second discount applies to the already reduced ₹1,400, giving ₹1,120, which is 44% off the original. Run it twice in the calculator (decrease by 30%, then decrease the result by 20%) and you'll see the real final price. The same logic applies to stacked taxes, fees and commissions: each percentage applies to whatever number it's taken from.
Quick mental shortcuts
10% is moving the decimal one place left; 5% is half of that; 1% is two places. So 15% of ₹840 is ₹84 plus ₹42, or ₹126. X% of Y also equals Y% of X, which makes 8% of 50 easier as 50% of 8: 4.
Privacy
According to the page, the numbers stay in the tab and aren't uploaded. Google ads appear on the page, as across the site.
FAQ
Why is percent change negative? The new number is smaller than the start.
Can I use decimals? Yes.
How do I add a percent to a number? Use Increase X by P%. ₹500 + 18% = ₹590.
Is percent change the same as percentage points? No. 10% to 12% is 2 points, a 20% change.
Settle the next percentage argument with Percentage calculator.
— Alok Kumar Singh