Percentage Calculator

What your result means

The big number is the answer to the calculation you chose; the sentence below it restates the question and answer in words so you can confirm you picked the right mode. Results are rounded to two decimal places.

X% of Y gives an amount (GST on a bill, commission, tip, interest for one period).
X is what % of Y gives a percentage (marks, attendance, market share).
% change compares an old and a new value (price rise, salary growth, fall in a share price).
Increase / decrease by % applies a percentage to a value (salary hike, discount, markup).
Original value before % reverses a percentage (price before GST, salary before a hike).

How to use this percentage calculator

Choose the type of calculation from the row of buttons.
Enter the two numbers. The field labels change to match the chosen mode.
For increase/decrease and reverse modes, pick the direction.
Read the answer and the plain-language explanation. Use Share or Print / PDF to keep it.

Formulas and worked examples

Every example below is computed by the same functions that power the calculator.

Question	Formula	Example
X% of Y	Y × X ÷ 100	18% of 2,500 = 450
X is what % of Y	X ÷ Y × 100	45 of 60 = 75%
% change from A to B	(B − A) ÷ A × 100	80 → 100 = +25%; 100 → 80 = -20%
Increase Y by X%	Y × (1 + X ÷ 100)	50,000 + 12.5% = 56,250
Decrease Y by X%	Y × (1 − X ÷ 100)	2,999 − 30% = 2,099.30
Original before X% increase	Final ÷ (1 + X ÷ 100)	1,180 incl. 18% GST → 1,000

Worked example (GST): a restaurant bill of ₹2,500 attracts 18% GST. 2,500 × 18 ÷ 100 = 450, so the total is ₹2,950. If instead you only know the total ₹1,180 and that it includes 18% GST, the base is 1,180 ÷ 1.18 = ₹1,000 and the GST component is ₹180.

Common percentages, ready reference

Use	Typical percentage	On ₹10,000
GST slabs	5%, 12%, 18%, 28%	500, 1,200, 1,800, 2,800
Typical salary hike	10%	1,000
Festival discount	30%	3,000 off → pay 7,000
Restaurant tip	10%	1,000

These are illustrations of the arithmetic only. Applicable GST rates depend on the goods or services and are set by the GST Council.

Special cases and common mistakes

Reverse percentages are not symmetric. A 30% discount followed by a 30% markup does not return to the original price: 100 → 70 → 91. Use the “Original value before %” mode to undo a percentage correctly.
Percentage vs percentage points. Going from 8% to 10% is +2 percentage points but a +25% change. Be clear which one you mean.
Negative starting values. Percentage change from a negative number (for example a loss turning into a profit) is ambiguous. The tool divides by the absolute value of the starting figure.
Dividing by zero. “What % of 0” and ”% change from 0” have no answer; the tool shows an error rather than a misleading number.
Compounding. Three successive 10% hikes are not 30% but 33.1%. Apply the increase mode three times, or use the SIP/EMI tools for compound interest.
Rounding. Results are rounded to two decimals. For large invoices, compute GST on the total rather than per line to avoid rounding drift, or follow your accountant’s practice.

Frequently asked questions

How do I calculate the percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 18% of ₹2,500 = 2,500 × 18 ÷ 100 = ₹450.

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. If you scored 45 out of 60, that is 45 ÷ 60 × 100 = 75%.

How is percentage increase or decrease calculated?

Subtract the old value from the new value, divide by the old value and multiply by 100. A rise from ₹80 to ₹100 is (100 − 80) ÷ 80 × 100 = 25% increase.

How do I remove GST from a total price?

Use the 'Original value before %' mode. If a bill of ₹1,180 includes 18% GST, the base price is 1,180 ÷ 1.18 = ₹1,000, and GST is ₹180. Do not simply subtract 18% of ₹1,180.

How do I calculate my marks percentage?

Add up the marks you obtained and the maximum marks across subjects, then use the 'X is what % of Y' mode with obtained marks as X and maximum marks as Y.

What is the difference between percentage and percentage points?

If interest rises from 8% to 10%, that is an increase of 2 percentage points but a 25% increase in the rate. The % change mode gives the latter.