Calculate any percentage instantly: marks, money, increase, decrease, difference, and percentage of a percentage. Step-by-step solutions with visual charts.
Example: 20% of 150 = 30
CSC Tool Hub's Percentage Calculator handles six calculation modes with step-by-step working, entirely in your browser. The math itself is simple; where people actually go wrong is in a handful of specific, common percentage traps — percentage points vs percentage change, successive percentage changes, and reverse tax calculations. This page covers those directly, since getting them wrong has real consequences on forms, bills and salary discussions.
If an interest rate rises from 5% to 7%, that is a rise of 2 percentage points — but it's also a 40% relative increase (2 ÷ 5 × 100). Both statements are true, but they mean very different things, and news headlines and marketing material frequently blur the two to make a change sound bigger or smaller than it is.
| Statement | What it actually means |
|---|---|
| "Interest rate up 2 percentage points" | Absolute change: 5% → 7% |
| "Interest rate up 40%" | Relative change: the rate itself increased by 40% of its original value |
Use the "% Increase" mode above for the relative version, and simple subtraction for percentage points.
This trips up a lot of people doing quick mental math on discounts or price changes. Take ₹100: a 10% increase makes it ₹110. A 10% decrease is then calculated on ₹110, not the original ₹100 — so it becomes ₹99, not ₹100. The two 10%s are never applied to the same base.
This matters directly for successive discounts (e.g. "20% off, plus an extra 10% off") — these don't add up to 30% off. A 20% discount followed by a 10% discount on the reduced price gives a combined discount of 28%, not 30%. Calculate each step separately rather than adding the percentages.
A common mistake: if a GST-inclusive price is ₹118 and GST is 18%, people often subtract 18% of ₹118 to find the original price. That's wrong, because 18% was calculated on the original price, not the final one.
The correct formula: Original Price = Final Price ÷ (1 + tax rate as a decimal). So ₹118 ÷ 1.18 = ₹100 — the correct original price, not ₹118 − ₹21.24 (which is what subtracting 18% of 118 gives).
Only if every semester or subject carries equal weight (same credits, same number of subjects). If one semester had more subjects or higher credit-weightage papers, a simple average of the percentages misrepresents your actual aggregate — a weighted average, where each percentage is multiplied by its weight (credits or marks) before averaging, is the correct approach. This is the same trap that causes confusion when converting CGPA to an aggregate percentage across unevenly-weighted semesters.
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Going from 5% to 7% is a rise of 2 percentage points, but a 40% relative increase (2/5 × 100). Headlines often blur the two.
No — it ends up lower than the original, because the 10% decrease is calculated on the new, larger value, not the original one.
Divide the final price by (1 + tax rate as a decimal). For ₹118 at 18% GST, the original price is 118 ÷ 1.18 = ₹100.
Only if each semester has equal weight. Otherwise use a weighted average based on credits or subject count, not a simple average.
No — they combine to 28% off, since the second discount applies to the already-reduced price.
Divide obtained marks by total marks and multiply by 100. Example: 450/500 × 100 = 90%.
Yes, completely free with no usage limits.
Yes — all calculations happen locally in your browser, nothing is sent to a server.
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