How to use this percentage calculator
- Percent of a number — type a percentage and a base value, then click Calculate to get the result. You can also leave any one of the three fields empty to solve for it.
- Common phrases — use the quick forms for “what is X% of Y,” “X is what % of Y,” and “X is Y% of what.”
- Percentage difference — compare two values using the symmetric difference formula (relative to their average).
- Percentage change — model an increase or decrease from a starting value, or work backward from a final amount.
What is a percentage?
A percentage expresses a number as a fraction of 100. The symbol % means “per hundred,” so 25% is the same as 25 per 100, or 0.25 as a decimal. Percentages are useful for discounts, tax rates, test scores, growth metrics, and any comparison scaled to a familiar base. New to the formulas? Read How to Calculate Percentage: Simple Formulas with Examples for step-by-step walkthroughs and practice problems.
Core percentage formula
The relationship between a percentage P, a base value V1, and a result V2 is:
When you type “25% of 80,” the calculator converts 25% to 0.25 and multiplies: 0.25 × 80 = 20.
Percentage difference vs. percentage change
Percentage difference compares two values symmetrically relative to their average. Percentage change measures movement from a starting point. Use change when you care about growth from a baseline; use difference when neither value is clearly the “original.”
Practical examples
- Sale price: 30% off $120 → enter 30% of 120 to get $36 off (final price $84).
- Test score: 42 correct out of 50 → “42 is what % of 50” → 84%.
- Pay raise: $55,000 increased by 4% → starting value 55000, increase 4%, result = $57,200.
Examples and use cases
Real-world use cases
- Retail markdown: A store manager verifies that a 25% clearance plus an extra 10% coupon matches the stacked discount math before updating signage.
- Grade improvement: A student calculates what score they need on a final exam to raise their course average from 78% to 85%.
- Business KPIs: A marketing lead measures month-over-month traffic growth as a percentage change to report campaign performance to leadership.