Percentage Calculator

Free online math tool

Calculate percentages, percentage changes, increases, decreases, original values, and shopping discounts with clear formulas and instant results.

Privacy-friendly: calculations happen locally in your browser. Your entered numbers are not sent to a server by this calculator.

Choose a calculation

What is X% of Y?

Enter a percentage and a number to calculate the percentage amount.

What Is a Percentage?

A percentage expresses a proportion out of 100. The symbol is %. For example, 25% means 25 out of every 100, which is equivalent to the decimal 0.25 and the fraction 1/4. Percentages make it easier to compare portions, prices, scores, and changes between values.

A percentage does not always have to be between 0% and 100%. A result above 100% can describe a value larger than a reference amount, while negative percentages can represent a decrease or a signed mathematical relationship.

How to Calculate a Percentage

Choose the formula that matches the question. The calculator above applies these formulas to your inputs and shows the working so you can check the result.

1. Percentage of a number

To find a percentage amount, convert the percentage to a fraction of 100 and multiply by the number.

Result = (Percentage ÷ 100) × Number

Example: 15% of 200 = 0.15 × 200 = 30.

2. Find what percentage one number is

Divide the part by the total, then multiply by 100. The total must not be zero.

Percentage = (Part ÷ Total) × 100

Example: 45 ÷ 300 × 100 = 15%.

3. Percentage increase or decrease

Subtract the original value from the new value and divide by the original value. Multiply by 100 to express the signed change as a percentage.

Change (%) = ((New − Original) ÷ Original) × 100

Example: From 80 to 100 is a 25% increase.

4. Increase or decrease a value

For an increase, multiply the starting value by one plus the percentage as a decimal. For a decrease, subtract the decimal percentage from one.

Increase = Original × (1 + Percentage ÷ 100) Decrease = Original × (1 − Percentage ÷ 100)

Example: 200 increased by 15% = 230; decreased by 15% = 170.

5. Find the original number

Divide the known result by the percentage expressed as a decimal. A zero percentage cannot be reversed this way.

Original = Known result ÷ (Percentage ÷ 100)

Example: If 30 is 15% of a number, the number is 30 ÷ 0.15 = 200.

6. Percentage difference

This calculator compares two values without treating one as the starting value. It divides their absolute difference by the average of their absolute magnitudes.

Difference (%) = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100

Example: Values 80 and 100 have a percentage difference of about 22.222222%.

7. Calculate a discount

Multiply the listed price by the discount percentage to find the saving, then subtract that saving from the listed price.

Saving = Price × Discount (%) ÷ 100 Sale price = Price − Saving

Example: A 25% discount on 80 saves 20, leaving a price of 60.

Everyday Percentage Examples

Shopping: A 20% discount on a price of 50 saves 10 before any taxes or additional charges.
Exam scores: A score of 72 out of 90 is (72 ÷ 90) × 100 = 80%.
Salary increase: A change from 40,000 to 42,000 is a 5% increase, calculated against the original amount.
Business growth: If monthly sales rise from 1,200 to 1,500, the increase is 25%.
Price decrease: A price falling from 160 to 120 has decreased by 25% of the original price.
Budgeting: If 300 of a 1,500 budget is spent, that spending represents 20% of the budget.

These examples illustrate the arithmetic only. Real invoices, taxes, discounts, salaries, and business figures may involve extra rules, rounding, fees, or deductions.

Percentage Reference Table

Percentage	Decimal	Fraction (simplified)
1%	0.01	1/100
5%	0.05	1/20
10%	0.1	1/10
12.5%	0.125	1/8
20%	0.2	1/5
25%	0.25	1/4
33.333…%	0.333…	1/3
50%	0.5	1/2
75%	0.75	3/4
100%	1	1/1
150%	1.5	3/2

Frequently Asked Questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply it by the number. For example, 20% of 150 is 0.20 × 150 = 30.

How do I calculate percentage increase?

Subtract the original value from the new value, divide that difference by the original value, and multiply by 100. For example, moving from 80 to 100 is a 25% increase.

What is the difference between percentage change and percentage difference?

Percentage change compares a new value with a specified original value, so the starting value matters. Percentage difference compares two values symmetrically, using their average magnitude as the reference in this calculator.

How do I calculate a discount?

Multiply the original price by the discount percentage divided by 100 to find the saving. Subtract the saving from the original price to find the discounted price.

Can a percentage be greater than 100%?

Yes. For example, 150% of 200 is 300. A percentage above 100% means the amount is greater than the full reference amount.

How can I find the original number from a percentage?

Divide the known result by the percentage expressed as a decimal. If 30 is 15% of a number, calculate 30 ÷ 0.15 = 200. The method cannot determine a unique original number when the percentage is zero.

Why is percentage change undefined when the original value is zero?

The percentage-change formula divides the difference by the original value. Division by zero is undefined, so a conventional percentage change cannot be calculated from a zero baseline.

Can I use decimals and negative numbers?

Yes. You can enter decimal values and negative values when appropriate. Interpret results carefully when the baseline is negative, because the sign of the conventional percentage change may not match the everyday description of the value moving up or down.

Does the currency selector convert currencies?

No. It changes only how the same numerical result is displayed. It does not use exchange rates and does not convert one currency into another.

Is this percentage calculator free to use?

Yes. The calculator is designed to be used directly in your browser without registration. Calculations are performed on your device by this widget.