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Five calculators in one: find a percentage of a number, work out what percent one number is of another, calculate percentage increase/decrease, adjust a number by a percentage, or compare two numbers directly.
Key Takeaways
- A percentage change and a percentage point change are not the same thing. Interest going from 10% to 15% is a 5 percentage point rise, but a 50% relative increase — mixing the two up is a common reporting error.
- Increasing then decreasing by the same percent doesn't return the original number. Raising 100 by 10% gives 110, but reducing 110 by 10% gives 99, not 100, because the second percentage is taken off a larger base.
- Percentage difference and percentage change answer different questions. Change assumes one value is the "before" and one is the "after"; difference treats two values as equals and compares them against their average.
What This Percentage Calculator Does
This is five percentage calculators combined into one tool, switchable with a tab: finding a percentage of a number, working out what percent one number is of another, calculating a percentage increase or decrease between two values, adjusting a number up or down by a percentage, and comparing two numbers as a percentage difference. Between them, these five modes cover the vast majority of everyday percentage questions — GST on a purchase, a discount at checkout, exam marks, a salary hike, a profit or loss margin, or comparing two prices or scores. Quick-select chips for common GST slabs (5%, 12%, 18%, 28%) and typical discount bands (10%, 20%, 50%) sit right above the first mode so the most frequent calculations in India take one tap instead of typing.
Everything runs entirely in your browser. No number you type is sent to a server, logged, or stored anywhere — close the tab and it's gone. There's no signup, no email wall, and no ads inside the calculator itself. Every calculation you run in a session is also logged to an on-page history list purely for your own reference during that visit, which you can export as a CSV or clear at any time; it is never saved once you leave the page.
How to Use This Percentage Calculator
Pick the tab that matches your question: % of a Number for "what is X% of Y", Reverse % for "A is what percent of B", % Increase/Decrease for the percent change between an old and a new value, Add/Subtract % to raise or lower a number by a percentage, and % Difference to compare two numbers as equals. Enter the numbers into the two fields for that mode — the result, a plain-language sentence, and the exact formula used update instantly with every keystroke, no "Calculate" button required.
A zero or blank denominator (dividing by a "whole" or "old value" of zero) isn't mathematically defined, so the calculator shows a dash instead of a result until you enter a non-zero value. Negative numbers are accepted in every mode — useful for percentage change questions where a value has gone down, which correctly returns a negative percentage. Use the Increase/Decrease toggle in the Add/Subtract tab to switch between raising and lowering a number by the entered percent.
The Percentage Formulas, Explained
All five modes come from the same underlying idea — a percentage is a fraction out of 100 — applied five different ways:
- % of a Number: Result = (Percent ÷ 100) × Number
- Reverse %: Percent = (Part ÷ Whole) × 100
- % Increase/Decrease: % Change = [(New − Old) ÷ Old] × 100
- Add/Subtract %: Result = Number × (1 ± Percent ÷ 100)
- % Difference: % Difference = [|A − B| ÷ ((A + B) ÷ 2)] × 100
Worked example (% of a Number): What is 18% GST on a purchase of INR 2,500?
- Percent ÷ 100 = 18 ÷ 100 = 0.18
- Result = 0.18 × 2,500 = INR 450
- So the GST-inclusive total would be 2,500 + 450 = INR 2,950
The same logic runs in reverse for the Reverse % tab (45 is 25% of 180), for % change (a price moving from 200 to 250 is a 25% increase), for Add/Subtract (increasing 800 by 15% gives 920), and for % Difference (120 and 150 differ by about 22.22% of their average).
Percentage Reference Table
A quick lookup for common GST and discount percentages against two round base amounts, useful for a fast sanity check without opening the calculator.
| Percent | Common Use | Value of INR 1,000 | Value of INR 10,000 |
|---|---|---|---|
| 5% | GST slab | INR 50 | INR 500 |
| 10% | Common discount | INR 100 | INR 1,000 |
| 12% | GST slab | INR 120 | INR 1,200 |
| 18% | GST slab | INR 180 | INR 1,800 |
| 20% | Common discount | INR 200 | INR 2,000 |
| 28% | GST slab | INR 280 | INR 2,800 |
| 50% | Half-price sale | INR 500 | INR 5,000 |
Quick Definitions
A percentage is a way of expressing a number as a fraction of 100, written with a "%" sign. A percentage point is the unit used when comparing two percentages directly — the difference between 40% and 45% is 5 percentage points, which is a different (and usually much smaller) figure than the 12.5% relative increase that same jump represents.
Frequently Asked Questions
Each percentage is calculated on a different base. Increasing 100 by 10% gives 110; decreasing that 110 by 10% removes 11 (10% of 110), leaving 99, not 100. The base shrinks or grows between the two steps.
Percentage change is a relative measure — how much something moved compared to its starting value. Percentage points is an absolute measure — the raw difference between two percentages. A rate moving from 5% to 10% is a 100% relative increase, but only a 5 percentage point rise.
Use the Reverse % tab with the GST amount as the "part" and the pre-tax price as the "whole" if you know both, or divide the final price by (1 + GST rate/100) to find the pre-tax amount if you only know the final price and the rate.
Percentage change treats one number as "before" and the other as "after," dividing by the original value. Percentage difference treats both numbers as equals with no direction, dividing the gap between them by their average instead.
Yes to both. A negative result in the % Change tab means a decrease rather than an increase. A result over 100% is normal whenever a number more than doubles, or when a part is larger than what it's being compared against.
No. The history list is held only in your browser's memory for the current page visit so you can review or export it, and is never transmitted or stored — refreshing or closing the tab clears it completely.