Percentage Calculator — Percent, % Change and Marks with Steps

What is a Percentage Calculator?

A Percentage Calculator (प्रतिशत कैलकुलेटर) answers the percentage questions that come up every day — in exams, shopping, salaries, business, banking and news. “Percent” means “per hundred”, so 25% simply means 25 out of every 100. The idea is simple, but it is easy to divide by the wrong number, forget which value is the base, or mix up a percentage change with percentage points.

This free calculator has six modes, each built for one specific question. You type two numbers, and it shows the answer together with the formula and every step of the working, so you can check it, learn the method or copy it into homework or a report. It handles decimals and negative numbers, and the link updates as you type so you can share the exact calculation.

Six Modes in One Tool

• X% of Y — what is 15% of 2,400? (Answer: 360)
• X is what % of Y — 360 is what percent of 2,400? (Answer: 15%)
• % change — the percentage increase or decrease from an old value to a new one.
• Marks % — marks obtained out of total marks, with a check that marks do not exceed the total.
• Add / subtract % — a number after adding or removing a percentage, such as a price plus 18% tax or minus 18% discount.
• X is Y% of what — find the whole when you know a part and its percentage.

How to Use It — Step by Step

1. Pick a mode from the buttons at the top.
2. Enter the two numbers. The box labels change to tell you what each number means in that mode.
3. Read the result in the large display, with the full working underneath.
4. Copy or share the result using the buttons.

Percentage Formulas with Worked Examples

Notice that percentage change always divides by the old value. A price that rises from 50 to 65 has increased by 30%, but if it then falls back from 65 to 50, that fall is only about 23.08% — because the base is now 65, not 50.

Mental Maths Shortcuts

• 10%: move the decimal point one place left — 10% of 3,450 is 345.
• 5%: half of 10% — 5% of 3,450 is 172.5.
• 1%: move the decimal two places left — 1% of 3,450 is 34.5.
• 25%, 50%, 75%: a quarter, a half and three quarters.
• Swap trick: X% of Y equals Y% of X. So 8% of 50 is the same as 50% of 8, which is 4.
• Build up: 18% = 10% + 5% + 3 × 1%. For 1,200: 120 + 60 + 36 = 216.

Percentages in Exams and Results

Students most often need the marks percentage: total marks obtained across all subjects divided by the maximum marks, multiplied by 100. If you scored 456 out of 500, your percentage is 91.2%. Some boards calculate the percentage on the best five subjects, and many universities give a CGPA instead of a percentage — for that, use our CGPA to Percentage converter. If your marks have different weightage (for example internal assessment 30% and the final exam 70%), use the weighted mode of our Average Calculator.

Percentages in Money

• Discounts: a 40% discount on ₹2,999 leaves 60%, which is ₹1,799.40. For stacked offers use the Discount Calculator.
• Tax: adding 18% GST multiplies the price by 1.18. Removing GST from a tax-inclusive price divides by 1.18 — not subtract 18%.
• Salary hike: a raise from ₹50,000 to ₹56,000 is a 12% increase.
• Interest: 8% a year on ₹1,00,000 is ₹8,000 a year in simple interest.
• Investment returns: buying at ₹200 and selling at ₹250 is a 25% gain.

Percentages, Fractions and Decimals

A percentage is just another way of writing a fraction or a decimal. Converting between them makes many problems easier: to use a percentage in a calculation, turn it into a decimal by dividing by 100; to express a decimal as a percentage, multiply by 100.

For fraction arithmetic with full steps, try our Fraction Calculator.

Successive and Reverse Percentages

When percentages are applied one after another, multiply the multipliers instead of adding the percentages. A 10% rise followed by another 10% rise gives 1.10 × 1.10 = 1.21, which is a 21% increase overall. A 20% discount followed by an extra 10% gives 0.80 × 0.90 = 0.72 — a 28% total discount, not 30%.

Reverse percentage problems ask for the value before a change. If a shirt costs ₹720 after a 20% discount, the original price is 720 ÷ 0.80 = ₹900. If your salary is ₹56,000 after a 12% raise, it was 56,000 ÷ 1.12 = ₹50,000 before. Always divide by the multiplier — subtracting the percentage from the new value gives the wrong answer because the percentage was taken of the original, not the new amount.

Real-World Uses

• Working out exam and assignment percentages.
• Checking whether a sale discount is genuine.
• Calculating tips, tax and service charges.
• Measuring growth in sales, followers, views or revenue month by month.
• Comparing prices that changed by different amounts.
• Calculating profit margin and markup in a small business.
• Understanding statistics and percentage changes reported in the news.
• Splitting costs or shares fairly between partners.

Common Mistakes to Avoid

• Dividing by the wrong base — percentage change uses the original (old) value.
• Adding successive percentages — a 10% rise followed by another 10% rise is 21% in total, not 20%.
• Expecting equal ups and downs to cancel — +50% then −50% leaves you 25% lower.
• Removing tax by subtracting the rate — ₹1,180 including 18% GST is ₹1,000 before tax, not ₹967.60.
• Confusing percent with percentage points — a rate moving from 4% to 6% is a 2-point rise but a 50% increase.
• Rounding too early — keep full precision until the final answer.

Tips and Troubleshooting

• “Y cannot be 0” — a percentage of zero is undefined; check that the whole is entered in the second box.
• “The old value cannot be 0” — percentage change from zero has no meaning; describe it as an absolute change instead.
• Negative results — in % change mode a negative answer means a decrease.
• Commas — type plain numbers such as 125000; the result is shown with digit grouping.
• Sharing — the page link keeps your numbers, so a classmate or colleague sees the same calculation.

Quick Glossary

• Percent (%): a number out of 100.
• Base / whole: the value the percentage is taken of.
• Part: the portion of the whole you are measuring.
• Percentage change: the relative change from an old value to a new one.
• Percentage point: the plain difference between two percentages.
• Multiplier: the factor to apply a percentage, such as 1.18 for +18% or 0.82 for −18%.

Why Use This Percentage Calculator?

Instead of one confusing box, you get a dedicated mode for each question, clear labels and the full working — ideal for students checking homework, shoppers checking discounts and professionals preparing reports. It is free, fast, accurate to four decimal places and runs privately in your browser on any device.

Percentage Calculator — Key Facts

Frequently Asked Questions

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