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Percentage Calculator
Calculate any percentage in seconds — what is X% of Y, percentage increase & decrease, tips, and discounts. Clean, fast, and built for mobile.
Also try loan / EMI, VAT, markup & margin, and compound interest.
Free percentage math with clear explanations
PercentBox is an educational site: every calculator ships with formulas, worked examples, and guides you can read without an account. Use the tool below for instant answers, or start with a step-by-step guide if you want to understand the method first.
What is X% of Y?
Find a percentage of a number
Quick select
Result
Enter values to calculate
How to use this percentage calculator
PercentBox is a free online percentage calculator designed for speed and clarity. Pick a mode, type your numbers, and get results instantly — no submit button needed. Perfect for schoolwork, shopping discounts, restaurant tips, markups, and everyday math.
What is X% of Y?
Find any percentage of a number. Example: What is 15% of 200? Answer: 30.
X is what % of Y?
Discover the relative size of two numbers. Example: 40 is 20% of 200.
Increase / Decrease
Raise or lower a value by a percent. Example: 100 increased by 12% = 112.
Percentage Change
Measure growth or decline from A to B. From 50 to 75 is a 50% increase.
Popular worked examples
Static examples search engines can index — open a tool to recalculate with your own numbers.
| Question | Answer |
|---|---|
| What is 15% of 200? | 30 |
| What is 20% of 50? | 10 |
| 25 is what % of 100? | 25% |
| Increase 80 by 25% | 100 |
| From 80 to 100 change | 25% |
| 18% tip on $64.50 | Tip $11.61 · Total $76.11 |
| 30% off $99.99 | Pay $69.99 · Save $30 |
Common percentage formulas
| Goal | Formula |
|---|---|
| X% of Y | (X ÷ 100) × Y |
| X is what % of Y | (X ÷ Y) × 100 |
| % increase / decrease (change) | ((new − old) ÷ |old|) × 100 |
| Value after % change | value × (1 ± percent/100) |
| Tip total | bill + bill × (tip% ÷ 100) |
| Sale price | price × (1 − discount%/100) |
Learn with free guides
Prefer a full explanation before you calculate? Our original guides walk through the same formulas used in the tools—with everyday examples for shopping, dining, school, and small business.
How to calculate percentages
Core formulas for percent of, reverse percent, increase, and change.
Increase vs percentage points
Why a “2% rise” and “2 percentage points” are not the same thing.
How to calculate a tip
Tip math, common rates, bill splitting, and mental shortcuts.
How to calculate discounts
Sale price, savings, and why stacked discounts are not additive.
Markup vs margin
Different denominators, worked example, and pricing formulas.
Compound interest basics
Simple vs compound interest and the standard growth formula.
How to calculate VAT
Add tax to net prices or extract VAT from gross totals correctly.
How loan EMI works
Fixed payments, amortization, and interest vs principal over time.
Mental math for percentages
Fast 10%/5%/15%/20% shortcuts for tips and discounts.
Common percentage mistakes
Wrong bases, percentage points mix-ups, and stacked discounts.
Why PercentBox is different
Many percentage tools show a single answer with little context. PercentBox pairs live calculators with formulas, static worked examples (so search engines and readers can verify the math), and longer guides when you want the “why.” Everything runs in your browser—no account required—and recent calculations stay on your device only.
We also cover related everyday finance math: VAT, markup and margin, compound interest, and loan / EMI estimates. Results are educational estimates; always confirm critical decisions with official sources or a professional.
Frequently asked questions
- How do I calculate a percentage of a number?
- Multiply the number by the percentage, then divide by 100. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. Use the “What is X% of Y?” mode above for instant results.
- How do I find what percent one number is of another?
- Divide the first number by the second, then multiply by 100. Example: 25 is what percent of 200? (25 ÷ 200) × 100 = 12.5%.
- How is percentage increase calculated?
- Percentage change = ((new − original) ÷ |original|) × 100. If a price goes from $80 to $100, the increase is ((100 − 80) ÷ 80) × 100 = 25%.
- How do I calculate a tip?
- Multiply the bill by the tip percentage divided by 100. An 18% tip on $64.50 is 0.18 × 64.50 = $11.61, for a total of $76.11. Our tip calculator can also split the bill.
- How do I calculate a discount?
- Savings = original price × (discount % ÷ 100). Final price = original − savings. A 25% off $79.99 item costs $59.99 and saves you $20.00.
- What is the difference between percentage change and percentage points?
- Percentage change is relative to the original value (e.g. from 10% to 15% interest is a 50% increase). Percentage points measure absolute difference (that same move is 5 percentage points).
- Can I use this percentage calculator on my phone?
- Yes. PercentBox is mobile-first and works in modern browsers on phones, tablets, and desktops without installing an app.
- Is PercentBox free to use?
- Yes. All calculators and guides are free, with no account or signup required. Ads may appear to support the site.
- Do you store the numbers I type?
- Calculations run in your browser. We do not require an account. Optional recent-history and theme settings stay in localStorage on your device only—you can clear them anytime.
- Are the results professional financial advice?
- No. Tools and articles are educational estimates. Loan, tax, and investment decisions should be confirmed with official documents or a qualified professional.
- Where can I learn the formulas in more depth?
- Open the Guides section for original explainers on percentages, tips, discounts, markup vs margin, and compound interest—then use the matching calculator to practice.
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