Percentage Calculator
Calculate percentages easily
Three calculation modes
Instant results
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Common examples
"What's 17.5% of $847?" Your brain freezes. "If sales went from 340 to 412, what's the percent increase?" Mental math breaks down.
Percentages lurk everywhere—discounts, tips, taxes, grades, statistics, business metrics. Yet despite being one of the most fundamental math concepts, most people struggle to calculate them quickly and accurately when the numbers aren't round and easy.
This isn't a weakness; it's just human. Calculators exist for a reason. This tool handles three types of percentage calculations instantly—so you can focus on decisions, not arithmetic.
What is a Percentage Calculator?
A Percentage Calculator solves the three most common percentage problems:
- What is X% of Y? — Find a portion (e.g., 15% of 200 = 30)
- X is what % of Y? — Find the ratio (e.g., 30 is 15% of 200)
- Percentage change from X to Y — Find growth/decline (e.g., 100 to 125 = 25% increase)
Core formulas:
X% of Y = Y Ă— (X / 100)
X is what % of Y = (X / Y) Ă— 100
% Change = ((New - Old) / Old) Ă— 100
For quick estimates: 10% is just moving the decimal one place left. 15% = 10%
- half of that. 20% = 10% doubled. These work for most everyday situations.
Why People Actually Need This Tool
A "50% increase" followed by a "50% decrease" doesn't return you to the original. 100 Ă— 1.5 = 150, then 150 Ă— 0.5 = 75. You're down 25%. Percentages on percentages require careful calculation.
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Shopping math — Calculate actual savings from "35% off" on a $78.99 item without a calculator app.
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Tip calculations — Go beyond 15-18-20% presets. What's the exact tip on $67.43 for exceptional service?
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Grade calculations — If you scored 42/50 on a test, what percentage is that? (84%)
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Business metrics — Calculate month-over-month growth, conversion rates, or profit margins.
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Investment returns — Your portfolio went from $12,500 to $14,200. What's the percentage gain?
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Statistical interpretation — Understand what "sales grew 12%" actually means in dollar terms.
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Cooking adjustments — Scale a recipe up 150% or down 75%.
How to Use the Percentage Calculator
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Select the calculation type:
- "What is X% of Y?" for finding portions
- "X is what % of Y?" for finding ratios
- "% Change" for comparing old to new values
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Enter your numbers — The tool labels fields clearly based on your selection.
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Get instant results — No submit button needed; calculations update as you type.
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Copy the result — Click to copy for use elsewhere.
| Calculation Type | Use Case | Example |
|---|---|---|
| X% of Y | Discounts, tips, taxes | 20% of $85 = $17 |
| X is what % of Y | Test scores, proportions | 72 out of 90 = 80% |
| % Change | Growth, decline | 80 to 100 = 25% increase |
20% of 100 = 20. But 20% increase ON 100 = 120. These are different calculations. Know which you need.
Real-World Use Cases
1. The Restaurant Bill Split
Context: A dinner bill is $156.78. The group wants to tip 22% and split 4 ways.
Problem: Mental math gets messy with these numbers.
Solution: 22% of $156.78 = $34.49 tip. Total = $191.27. Per person = $47.82.
Outcome: Everyone pays fair share without over- or under-tipping.
2. The Test Score Conversion
Context: A student scored 67 out of 80 points. They need to know their percentage.
Problem: 67/80 isn't intuitive.
Solution: 67 is what % of 80? → (67 ÷ 80) × 100 = 83.75%
Outcome: The student knows their grade instantly.
3. The Sales Growth Report
Context: Q1 revenue was $245,000. Q2 is $289,000. The boss wants percentage growth.
Problem: Calculating change between non-round numbers.
Solution: % change from 245,000 to 289,000 = 17.96% increase.
Outcome: The CEO gets a clear, accurate metric for the board meeting.
4. The Discount Verification
Context: A laptop is listed at $1,299. Sale sign says "Save 18%."
Problem: Is the $230 claimed savings accurate?
Solution: 18% of $1,299 = $233.82. Sale price should be ~$1,065.
Outcome: The shopper verifies the math or catches a pricing error.
5. The Ingredient Scaling
Context: A recipe for 6 servings needs to serve 15 people.
Problem: What percentage increase is needed? (15/6 = 2.5x or 150% of original)
Solution: Calculate 150% of each ingredient. 2 cups flour → 3 cups.
Outcome: The cook scales accurately without guessing.
6. The Raise Negotiation
Context: Current salary is $72,000. Job offer is $81,000.
Problem: What percentage raise is that?
Solution: % change from 72,000 to 81,000 = 12.5% increase.
Outcome: The candidate can compare offers accurately and negotiate from data.
7. The Weight Loss Tracker
Context: Starting weight 195 lbs, current weight 178 lbs.
Problem: What percentage of body weight has been lost?
Solution: 17 is what % of 195? = 8.7% body weight lost.
Outcome: The person tracks progress with meaningful metrics.
Common Mistakes and How to Avoid Them
Most percentage errors come from confusing "percent of" with "percent change" or forgetting what the base number should be.
Privacy and Data Handling
This Percentage Calculator runs entirely in your browser. Simple as that.
- No numbers are transmitted anywhere.
- No calculation history is stored.
- No account needed.
- Works completely offline.
Do your math in private.
Conclusion
Percentages are fundamental to making sense of the world—prices, performance, progress, proportions. But human brains aren't wired for quick percentage calculations, especially with messy real-world numbers.
This calculator handles the math so you can make decisions. Whether you're checking a sale price, calculating a tip, measuring growth, or solving homework, the answer is one input away.
Stop second-guessing your mental math. Get the number right, instantly.