Free Percentage Calculator
Calculate percentages in four modes: find X% of a number, find what percent X is of Y, calculate percentage change between two values, and find the original value from a percentage. Free, private — all calculations run in your browser.
A% × B📊 All Calculations for A=25, B=200
About This Percentage Calculator
Percentages are one of the most universally useful mathematical concepts — appearing in retail discounts, tax calculations, test scores, salary raises, investment returns, survey statistics, and countless other everyday situations. This Percentage Calculator covers all three fundamental percentage problem types, plus a reverse percentage mode, so you can solve any percentage question you encounter with a single tool.
The Formulas — How It Works
The calculator provides four distinct calculation modes, each using a specific formula:
Mode 2: X is what % of Y? → Result = (X ÷ Y) × 100
Mode 3: % change (Old to New) → ((New − Old) ÷ Old) × 100
Mode 4: Reverse % (find original) → Original = Result ÷ (X ÷ 100)
Mode 1 answers: "What is 15% of $240?" (= $36). Mode 2 answers: "15 is what percent of 60?" (= 25%). Mode 3 answers: "What is the percentage change from $80 to $100?" (= +25%). Mode 4 answers: "$45 is 30% of what number?" (= $150).
Key Concepts and Common Pitfalls
Several percentage concepts trip people up even when the arithmetic is straightforward:
- •Percentage vs percentage point: a rate rising from 5% to 7% is a 2 percentage-point increase but a 40% increase in the rate
- •Compounding: 20% off then 10% off is NOT 30% off — it is 0.80 × 0.90 = 28% off
- •Asymmetry: a 50% loss requires a 100% gain to recover (not 50%)
- •Base matters: "20% more than X" and "X is 20% more than Y" have different base values
- •Percentage of a percentage: "10% of 20%" = 2%, not 30% (you multiply: 0.10 × 0.20 = 0.02)
Who Should Use This Calculator
This tool is for everyone — students checking homework, shoppers comparing discounts, employees calculating commission or raise percentages, business analysts computing margins and growth rates, teachers grading assessments, and anyone who encounters a percentage problem in daily life. Unlike a standard calculator, this tool frames the problem in human terms ("what is X% of Y?") so you can select the right mode without having to remember which formula applies.
Privacy Notice
All calculations in this percentage calculator are performed entirely in your browser. No inputs you enter are transmitted to any server, stored in any database, or shared with third parties. See our Privacy Policy for full details.
When to Use This Calculator
Instantly calculate what 25% off a $79.99 item costs, or find what percentage you are saving when a $120 item is marked down to $89 — without needing to do long division in the store.
Calculate 8.25% sales tax on a purchase, find 18% tip on a restaurant bill, or determine the pre-tax price when you know the after-tax total.
Find what percentage you scored on a test, calculate what grade a curve adds to a raw score, or determine the minimum raw score needed to earn a target percentage grade.
Calculate percentage change between two data points, find what portion of a total a segment represents, or compute year-over-year growth rates for business reporting.
Calculate gross margin percentage, find markup from cost to price, determine commission amounts, or evaluate what percentage of revenue represents each expense category.
💡 Pro Tips
Always distinguish between percentage change and percentage point change. Politicians, journalists, and marketers often blur this intentionally. "Unemployment fell from 6% to 4%" — that is 2 percentage points, but a 33% decrease in the unemployment rate. Use this calculator to verify which meaning is being communicated and whether the framing favors the speaker's argument.
To multiply percentages, convert to decimals first and multiply — never add percentages together. To apply a 15% discount and then an 8% sales tax, calculate: Price × 0.85 × 1.08. Adding 15% − 8% = 7% and applying that single adjustment gives a different (wrong) answer. The correct combined factor is 0.85 × 1.08 = 0.918 (an 8.2% net reduction).
Beware the "percent of percent" trap. If a store offers 50% off a 20%-off item, the discount is NOT 70% off. It is 50% off the already-discounted price: if original is $100, then 20% off = $80, then 50% off $80 = $40 — which is 60% off the original, not 70%. This calculator handles each step correctly when you apply them sequentially.
For mental math shortcuts: find 10% by moving the decimal one place left ($75 → $7.50). Find 5% by halving 10%. Find 15% by adding 10% and 5%. Find 25% by dividing by 4. Find 1% by moving the decimal two places left. Combining these mental shortcuts you can estimate most common percentages in seconds — then verify with this calculator for precision.
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