How to Use the Percentage Calculator

Choose the type of percentage calculation you need and enter the required numbers. The calculator updates automatically and shows both the answer and the formula used.

You can calculate:

• What is X percent of Y;
• X is what percentage of Y;
• Percentage increase;
• Percentage decrease;
• A number increased by a percentage;
• A number reduced by a percentage; and
• The original number before a percentage increase or decrease.

How Do You Calculate a Percentage of a Number?

To calculate a percentage of a number:

For example, to calculate 20% of 150:

Therefore, 20% of 150 is 30.

Percentage Calculator Example

How Do I Find What Percentage One Number Is of Another?

Use:

For example, if 30 out of 120 people selected an option:

Therefore, 30 is 25% of 120.

What Percentage Is 50 of 200?

So 50 is 25% of 200.

How Do You Calculate Percentage Increase?

Percentage increase compares the increase with the original value.

For example, if a price increases from $80 to $100:

Difference:

100 − 80 = 20

Percentage increase:

How Do You Calculate Percentage Decrease?

For a decrease:

For example, if a price falls from $200 to $150:

Difference:

200 − 150 = 50

Percentage decrease:

Percentage Change Formula

A general percentage-change formula is:

A positive result represents an increase, while a negative result represents a decrease.

For additional change-focused calculations, use the Percentage Change Calculator.

How to Add a Percentage to a Number

To increase a number by a percentage:

For example, increase $500 by 10%:

The new value is $550.

How to Subtract a Percentage From a Number

To decrease a number by a percentage:

For example, reduce $500 by 10%:

How to Calculate a Discount Percentage

To calculate the amount saved from a discount:

Then:

For example, a $120 item with a 25% discount has a discount of:

120 × 25% = $30

Sale price:

$120 − $30 = $90

How to Add GST Using Percentages

In Australia, GST is commonly calculated as 10% of the GST-exclusive price for taxable supplies.

For a GST-exclusive amount of $100:

GST-inclusive amount:

$100 + $10 = $110

For a dedicated calculation, use the Australia GST Calculator.

How Do I Find the Original Value Before a Percentage Increase?

If a value has already increased by a known percentage:

For example, a value is $120 after a 20% increase:

The original value was $100.

How Do I Find the Original Price Before a Discount?

If a final price represents the original price after a percentage decrease:

For example, a product costs $80 after a 20% discount:

The original price was $100.

Why Doesn’t Adding and Subtracting the Same Percentage Cancel Out?

Because the second percentage is applied to a different base value.

For example, increasing 100 by 20% gives:

100 → 120

Reducing 120 by 20% gives:

120 × 0.80 = 96

The result is 96, not 100.

Percentage vs Percentage Points

A percentage change and a percentage-point change are not the same thing.

Suppose an interest rate rises from 4% to 5%.

The increase is:

• 1 percentage point; but
• 25% relative increase.

The relative increase is:

How to Calculate Exam Percentages

If you score 42 marks out of 50:

For multiple assessments and weighted grades, use the Grade Percentage Calculator.

How to Calculate Percentage Profit

A simple percentage return calculation can be expressed as:

If an investment increases from $1,000 to $1,200:

Profit:

$200

Percentage return:

How to Calculate Percentage Difference

Percentage difference is often used when comparing two values where neither is specifically considered the original value.

This is different from percentage change, where one value is explicitly the original or starting value.

Common Percentage Conversions

Percentages can be converted into decimals by dividing by 100.

• 1% = 0.01;
• 5% = 0.05;
• 10% = 0.10;
• 20% = 0.20;
• 25% = 0.25;
• 50% = 0.50;
• 75% = 0.75;
• 100% = 1.00;
• 150% = 1.50; and
• 200% = 2.00.

What Does 100% Mean?

100% represents the entire amount.

For example:

100% of 250 = 250

What Does More Than 100% Mean?

A percentage can be greater than 100%.

For example:

This represents one and a half times the original amount.

Can a Percentage Be Negative?

Yes. Negative percentages can be meaningful in some calculations, particularly percentage change.

For example, a change from 100 to 80 is:

The negative sign represents a decrease.

Percentage Calculator Assumptions

This calculator assumes:

• Entered values are numeric;
• Percentage calculations use standard mathematical formulas;
• Percentage change uses the first value as the original value;
• Division by zero is not valid;
• Results can contain decimals;
• Financial examples do not include fees or taxes unless explicitly stated;
• Rounding is for display purposes only; and
• Results are general mathematical calculations.

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