How do I calculate percentage of a number?

Multiply the number by the percentage and divide by 100. Example: 50% of 200 = (200 × 50) ÷ 100 = 100. Our calculator does this instantly.

How do I add or subtract a percentage?

To add 20% to 100, calculate 20 and add it to get 120. To subtract 20%, subtract 20 to get 80. Use the Increase by % or Decrease by % mode for these operations.

What's the difference between percentage change and percentage point?

Percentage change: 20 to 30 is a 50% increase. Percentage point: moving from 20% to 30% is a 10 percentage point increase (not 10% increase).

Can this calculator recover an unknown original value or rate?

No. It can apply an entered increase or decrease to a known starting value, but it does not reverse a changed result to recover an unknown original value or unknown rate.

Percentage Calculator Guide: Master Percentage Calculations

What is a Percentage?

A percentage is a number expressed as a fraction of 100. The word "percent" literally means "per hundred." For example, 50% means 50 out of 100, which equals 0.50 in decimal form. APercentage Calculator is useful for quick checks.

What the Live Calculator Supports

Find X% of Y
Find what percent X is of Y
Calculate percentage change from an old value to a new value
Increase a known starting value by an entered percentage
Decrease a known starting value by an entered percentage

It does not currently recover an unknown whole, original value, or percentage rate from a changed result.

Basic Percentage Formulas

Find a Percentage of a Number

Percentage = (Part ÷ Whole) × 100

Find a Percentage Value

Value = Whole × (Percentage ÷ 100)

Manual Formula: Find the Whole from a Percentage

Whole = Part ÷ (Percentage ÷ 100)

This reverse formula is included for reference, but finding an unknown whole is not one of the live calculator's five modes.

Percentage Calculation Examples

Example 1: Calculate a Percentage

What percentage is 25 out of 200?

Percentage = (25 ÷ 200) × 100 = 12.5%

Example 2: Find a Percentage Value

What is 20% of $500?

Value = 500 × (20 ÷ 100) = $100

Manual Example 3: Find the Whole

If 30% of a number is 60, what is the number?

Whole = 60 ÷ (30 ÷ 100) = 200

Work this example with the formula shown above; the current calculator does not provide an unknown-whole input mode.

Percentage Change

Percentage change measures how much a value has increased or decreased relative to its original value.

Percentage Increase Formula

% Increase = ((New Value - Old Value) ÷ Old Value) × 100

Percentage Decrease Formula

% Decrease = ((Old Value - New Value) ÷ Old Value) × 100

Percentage Change Examples

Example 1: Percentage Increase

Stock price increased from $50 to $75. What's the percentage increase?

% Increase = ((75 - 50) ÷ 50) × 100 = (25 ÷ 50) × 100 = 50%

Example 2: Percentage Decrease

Product weight decreased from 100g to 85g. What's the percentage decrease?

% Decrease = ((100 - 85) ÷ 100) × 100 = (15 ÷ 100) × 100 = 15%

Real-World Percentage Applications

Sales Tax Calculation

If an item costs $100 and sales tax is 8%, the tax amount is:

Tax = 100 × (8 ÷ 100) = $8
Total Price = $100 + $8 = $108

Tip Calculation

For a $50 restaurant bill with a 20% tip:

Tip = 50 × (20 ÷ 100) = $10
Total = $50 + $10 = $60

Test Score Percentage

If you got 45 questions correct out of 50 on a test:

Score = (45 ÷ 50) × 100 = 90%

Salary Increase

If your salary increased from $40,000 to $44,000:

% Increase = ((44,000 - 40,000) ÷ 40,000) × 100 = 10%

Percentage Points vs. Percentages

These are often confused but are different:

Percentage: A number out of 100. Example: 50%
Percentage Points: The difference between two percentages. Example: If approval rating rises from 30% to 45%, it increased by 15 percentage points (not 15%).

Common Percentage Mistakes

Reversing Increase/Decrease

A 50% increase followed by a 50% decrease does NOT return you to the original value. A $100 item increased by 50% becomes $150, then decreased by 50% to $75, not $100.

Confusing Percentage with Percentage Points

Saying "interest rates increased 2 percent" is ambiguous. Always clarify: "rates increased 2 percentage points" or "rates increased by 2%."

Using the Wrong Base

Always calculate percentages using the correct base number. For percentage change, use the original value, not the new value.

Forgetting to Multiply by 100

When calculating a percentage, always multiply by 100 to get the percentage value.

Percentage Shortcuts

Calculate 10%

Move the decimal point one place to the left. 10% of $85 = $8.50

Calculate 1%

Move the decimal point two places to the left. 1% of $85 = $0.85

Calculate 50%

Divide by 2. 50% of $80 = $40

Calculate 25%

Divide by 4. 25% of $80 = $20

Calculate 20%

Divide by 5. 20% of $100 = $20

Conclusion

Percentages are everywhere in daily life-from shopping discounts to salary raises to test scores. Our Percentage Calculator handles the five supported value-of, comparison, change, increase, and decrease operations.

Use the Percentage Calculator when your problem matches one of those modes. Use a separate reverse formula when the original value, whole, or rate is unknown.