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Percentage Calculator

Free online percentage calculator for everyday math — find what percent of a number is, calculate percentage change between two values, work out discounts, or project a new value after a percentage increase. Instant results, no sign-up required.

What is X% of Y?

%

Result

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How to Use the Percentage Calculator

X% of Y

Enter any percentage and number to get the result instantly. Example: 15% of 200 = 30.

X is what %?

Find what percentage one value is of another. Example: 45 is what % of 180? → 25%.

% Change

Enter old and new values to see the percentage increase or decrease. Negative result = decrease.

% Off

Enter original price and discount percentage. Shows final price and exact savings amount.

Percentage Formulas

CalculationFormulaExample
X% of Y(X ÷ 100) × Y20% of 50 = 10
X is what % of Y(X ÷ Y) × 10030 of 120 = 25%
% Change((New − Old) ÷ |Old|) × 10080 → 100 = +25%
% OffPrice × (1 − Discount ÷ 100)$200 − 10% = $180
% IncreaseOriginal × (1 + Rate ÷ 100)500 + 20% = 600

Reverse Percentage Calculator

A reverse percentage works backwards — you know the result and the percentage applied, and you need to find the original value. Common use cases: finding pre-tax price, pre-discount original price, or pre-raise salary.

Formula: Original = Result ÷ (1 ± Rate ÷ 100)

After a 20% increase → find original

Original = Final ÷ 1.20

Example: $120 after 20% raise → $120 ÷ 1.20 = $100

After a 25% discount → find original

Original = Final ÷ 0.75

Example: $75 after 25% off → $75 ÷ 0.75 = $100

Price after 10% VAT → find pre-tax

Pre-tax = Final ÷ 1.10

Example: $55 incl. 10% tax → $55 ÷ 1.10 = $50

Score after 15% penalty → find original

Original = Final ÷ 0.85

Example: 85 pts after 15% deduction → 85 ÷ 0.85 = 100

Use the % Change tab above and enter your final value as "New" and original as "Old" to verify any reverse calculation.

How to Calculate a Percentage Discount

Discount calculations are the most common use for percentage math — comparing sale prices, stacking coupons, or checking if a "deal" is actually a good deal.

ScenarioFormulaExample
Final price after X% offPrice × (1 − X/100)$80 × 0.70 = $56 (30% off)
How much you savePrice × (X/100)$80 × 0.30 = $24 saved
What % off is the sale?((Original − Sale) ÷ Original) × 100($100 − $65) ÷ $100 = 35% off
Stacked discounts (10% then 20%)Price × 0.90 × 0.80$100 → $90 → $72 (not 30% off!)
Tip: Stacked discounts are NOT additive. Two 10% discounts = 19% off total (not 20%) because the second discount applies to the already-reduced price.

Frequently Asked Questions

How do I calculate what percent of a number is?▾
To find X% of Y, multiply Y by X and divide by 100. Example: 20% of 150 = (20 ÷ 100) × 150 = 30. Use the "X% of Y" tab above for instant results.
How do I calculate percentage change between two numbers?▾
Percentage change = ((New Value − Old Value) ÷ |Old Value|) × 100. A positive result is an increase, negative is a decrease. Example: from 80 to 100 = ((100−80) ÷ 80) × 100 = 25% increase.
How do I calculate a percentage discount?▾
Final price = Original Price × (1 − Discount% ÷ 100). Example: $200 with 15% off = 200 × 0.85 = $170. Savings = 200 × 0.15 = $30. Use the "% Off" tab for instant calculation.
What is percentage increase?▾
Percentage increase finds the new value after adding a percentage to the original. Formula: New Value = Original × (1 + Rate ÷ 100). Example: 500 increased by 12% = 500 × 1.12 = 560.
How do I find what percentage X is of Y?▾
Divide X by Y and multiply by 100. Example: 45 out of 180 = (45 ÷ 180) × 100 = 25%. Use the "X is what %?" tab.
What is the difference between percentage change and percentage increase?▾
Percentage change measures how much a value changed relative to the original (can be positive or negative). Percentage increase gives you the new absolute value after applying a growth rate. Use % Change for comparison; use % Increase to project a new value.
How do I reverse a percentage — find the original price before a discount?▾
If you know the final price and discount rate: Original = Final Price ÷ (1 − Discount% ÷ 100). Example: $85 after 15% off → 85 ÷ 0.85 = $100 original.
Is this percentage calculator accurate?▾
Yes. All calculations use standard JavaScript floating-point arithmetic with results rounded to 6 decimal places to avoid display noise. Results are equivalent to formula-based spreadsheet calculations.