What is a percentage?
A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin per centum, meaning out of a hundred. If you score 70 out of 100 on a test, that is 70%. If a shop marks a price down by 20%, it means the discount is twenty rupees for every hundred rupees of the original price. Percentages are one of the most widely used tools in everyday mathematics because they turn ratios into easy-to-compare numbers, no matter how large or small the underlying quantities are.
This percentage calculator handles the three most common percentage tasks instantly: finding a percentage of a number, adding a percentage to a number and subtracting a percentage from a number. It returns all three results at once, so you never have to switch between tools or redo your arithmetic.
How to use this percentage calculator
- Enter the value you want to work with, such as a price, bill, score or salary.
- Enter the percentage, for example 15 or 18 or 7.5.
- Read the three results: the exact amount that percentage represents, the value after adding the percentage, and the value after subtracting it.
Because the calculator works with decimal percentages, you can enter values like 7.5% or 12.25% and still get an exact answer.
How percentages are calculated
The core operation is simple: multiply the value by the percentage and divide by 100. Finding 15% of 250 means computing 250 × 15 ÷ 100, which is 37.5. Adding a percentage uses the factor (1 + percentage/100), so adding 18% to a value means multiplying it by 1.18. Subtracting a percentage uses the factor (1 − percentage/100), so applying a 20% discount means multiplying by 0.80. The calculator applies these three operations automatically and shows you all the answers.
Everyday uses of percentages
- Shopping: calculating sale discounts and comparing deals where prices have been reduced by different percentages.
- Taxes: working out GST, VAT, service tax or sales tax added on top of a price.
- Tips and bills: adding a 10% or 15% tip when splitting a restaurant bill.
- Finance: understanding interest rates, loan fees and annual percentage rates on investments.
- Education: converting test scores and marks into percentages for comparisons.
- Statistics: expressing shares, growth rates and survey results as percentages.
Converting fractions and decimals to percentages
To convert a fraction to a percentage, divide the numerator by the denominator and multiply by 100. For example, 3/4 equals 0.75, which is 75%. To convert a decimal, simply move the decimal point two places to the right and add the percent sign, so 0.45 becomes 45%. These conversions are the building blocks of almost every percentage problem you will meet.
Finding what percentage one number is of another
A very common question is: what percentage is A of B? The answer is A ÷ B × 100. If 25 out of 200 items have been sold, the sold share is 25 ÷ 200 × 100, which is 12.5%. If your salary increased from ₹40,000 to ₹46,000, the increase of ₹6,000 represents 6,000 ÷ 40,000 × 100, or 15% of your old salary. This type of calculation is invaluable for understanding growth, market share and proportional change.
Calculating percentage increases and decreases
When a quantity changes, the percentage change is the difference divided by the original value, multiplied by 100. A price that rises from ₹200 to ₹250 increased by 25%, because 50 ÷ 200 × 100 equals 25. A price that falls from ₹250 to ₹200 decreased by 20%, because 50 ÷ 250 × 100 equals 20. Notice that the two directions are not symmetric — the percentages are computed on different bases — which is why a 25% increase followed by a 20% decrease returns you exactly to the original price.
A caution about percentage reversibility
Percentages are not reversible in the way you might expect. A 50% discount followed by a 50% increase does not restore the original price. If something costs ₹100 and drops 50%, it becomes ₹50; a 50% increase then takes it to ₹75, not ₹100, because the increase is calculated on the smaller amount. This principle matters in investing, shopping and negotiating, where sequential percentage changes are common. Always apply percentage changes to the current value, not to the starting value.
Why a percentage calculator saves you mistakes
Doing percentages by hand is easy to get wrong, especially with odd figures, decimal percentages or multiple steps in a single calculation. A calculator eliminates arithmetic slips and gives you a consistent answer every time. When you need to check a bill, compare a loan offer or set a pricing discount, having the percentage amount, the increased value and the decreased value visible together lets you sanity-check the numbers before committing to them.
Percentage points versus percentages
There is an important distinction between a percentage and a percentage point, especially in finance and economics. If an interest rate rises from 8% to 9%, it has increased by one percentage point. But relative to the old rate, it has increased by 12.5%, because 1 divided by 8 multiplied by 100 equals 12.5. News reports often blur these two, so it pays to read carefully. When a bank says its deposit rate went up by one percent, it might mean one percentage point or a one percent relative rise, and the two are very different. This calculator can help you convert between the two interpretations for whatever figures you are working with.
Percentages in finance and interest
Interest rates are always stated as percentages, but the way they apply depends on whether the rate is simple or compound. Simple interest of 10% a year on ₹10,000 produces ₹1,000 every year. Compound interest of 10% builds on the previous balance, so the amount of interest grows each year. When you see a loan or investment described with a percentage rate, check whether the percentage is added once or compounded repeatedly, because the two produce very different totals over time. This percentage calculator handles the single-step percentage arithmetic, which is the building block for understanding both.
Worked examples with this calculator
Put the calculator to work on realistic scenarios. A laptop costs ₹48,000 and is on sale at 20% off. The discount is ₹9,600, bringing the price to ₹38,400 — enter 48000 with 20 and read the subtraction result. A restaurant bill is ₹2,400 and you want to tip 10%: the tip is ₹240 and the total is ₹2,640. A product price of ₹500 needs 18% GST added, which gives ₹90 of tax and a final price of ₹590. Each of these is a single entry with this tool, and having all three results visible lets you double-check your working.
Percentages and ratios in everyday life
Percentages also underpin ratios you encounter constantly: batting and bowling averages, exam cut-offs, election vote shares, survey results, humidity, alcohol by volume and nutritional figures on food labels all rely on the same out-of-a-hundred logic. Once you are comfortable moving between fractions, decimals and percentages, these numbers become easy to read and compare. The calculator is a quick check whenever you are in a hurry and want to avoid mental arithmetic errors.
Limitations and notes
Percentages describe proportions, but they do not tell you the size of the underlying quantities. A 50% discount on a very expensive item can still be a large absolute amount, while 50% off something cheap is small. Always consider both the percentage and the actual numbers involved. This calculator is accurate for straightforward percentage arithmetic; for compound or sequential percentage changes, work through each step in order.