Percentage Calculator
Percentage Calculator
Find a portion of a whole.
Result
Computed calculation result.
Computation Guide
Calculates the portion of a number. Useful for finding discounts, taxes, or partial quantities.
Determines what fraction one number is of another, expressed as a percentage.
Finds the relative change between an old and new value. Negative values indicate a decrease.
Percentage Calculator
How to Use
- 1Choose a calculation mode: '% of Value' to find a portion, 'What %' to find the percentage, '% Change' for increase/decrease, or 'Reverse %' to find the original value before a percentage was applied.
- 2Enter the known values into the input fields.
- 3Results appear instantly with a step-by-step breakdown showing exactly how the answer was calculated.
Formula & Logic
A percentage expresses a number as a fraction of 100. The four core percentage operations are: finding a percentage of a value, finding what percentage one number is of another, calculating percentage change between two numbers, and reversing a percentage to recover the original value before a change was applied.
Practical Applications
Shopping & Discounts
Calculate the sale price after a discount, or use reverse percentage to find the original price before a discount was applied — useful when a store shows only the final discounted price.
Finance & Profit Margins
Determine profit percentage from cost and selling price, calculate markup amounts, or find the percentage increase between last quarter's revenue and this quarter's.
Statistics & Data Analysis
Compute percentage change between data points, including negative values when a metric decreases. Useful for year-over-year growth, survey results, and performance tracking.
Education & Grading
Convert raw scores to percentages, find what percentage a student scored, or calculate how much a score improved between two tests.
Frequently Asked Questions
QHow do I calculate percentage increase step by step?
Step 1: Subtract the original value from the new value to get the difference. Step 2: Divide that difference by the original value. Step 3: Multiply by 100. Example: from 80 to 100 → (100 − 80) ÷ 80 × 100 = 25% increase. Use the '% Change' mode above.
QHow do I find the original price before a discount (reverse percentage)?
Divide the final price by (1 − discount rate / 100). Example: if an item costs $80 after a 20% discount, the original price is $80 ÷ (1 − 0.20) = $80 ÷ 0.80 = $100. Use the 'Reverse %' mode and select 'discount'.
QHow do I calculate the percentage difference between two numbers?
Percentage difference = |Value1 − Value2| ÷ ((Value1 + Value2) / 2) × 100. For directional change (increase/decrease), use percentage change instead: (New − Old) ÷ |Old| × 100.
QHow do I calculate profit percentage from cost and selling price?
Profit % = ((Selling Price − Cost Price) ÷ Cost Price) × 100. Example: cost $50, selling price $65 → profit = $15, profit % = (15 ÷ 50) × 100 = 30%. Use 'What %' mode with part = profit and total = cost.
QHow do I apply multiple discounts one after another?
Apply each discount sequentially, not additively. Example: 20% off then 10% off a $100 item → $100 × 0.80 = $80, then $80 × 0.90 = $72. The combined effective discount is 28%, not 30%. Use '% of Value' mode for each step.
QCan percentage change be negative?
Yes. A negative percentage change means the value decreased. Example: from 200 to 150 → (150 − 200) ÷ 200 × 100 = −25%. The calculator displays decreases in red and increases in green.
QHow much percent increase is there between two numbers?
Use the formula: ((New − Old) ÷ Old) × 100. Example: from 50 to 75 → ((75 − 50) ÷ 50) × 100 = 50% increase. Enter the values in '% Change' mode for an instant result with steps.
QHow do I calculate a percentage of a number with steps?
Step 1: Divide the percentage by 100 to convert it to a decimal. Step 2: Multiply by the total. Example: 15% of 200 → 15 ÷ 100 = 0.15, then 0.15 × 200 = 30. The calculator shows each step automatically.
QWhat is the percentage difference formula used online?
For percentage change: ((New − Old) / |Old|) × 100. For symmetric percentage difference: |A − B| / ((A + B) / 2) × 100. This calculator uses the percentage change formula, which gives directional results (positive or negative).
QHow do I quickly calculate a percentage in my head?
Use these shortcuts: 10% = move decimal one place left. 5% = half of 10%. 25% = divide by 4. 50% = divide by 2. 1% = move decimal two places left. For 15%, find 10% and add half of it. Combine these for fast mental math.