Percentage Calculator
Solve any percentage problem in seconds — right in your browser. This free percentage calculator handles the everyday questions people actually ask: what is X% of a number, what percent one number is of another, and the percentage increase or decrease between two values. Enter your numbers and get an instant, accurate answer. It's perfect for discounts, tips, taxes, grades, and quick math. Everything runs locally on your device — nothing you enter is uploaded or stored. No signup, no limits.
About Percentages
A percentage is a way of expressing a number as a fraction of 100 — the word literally means "per hundred." It's one of the most useful math concepts in daily life, showing up in discounts, taxes, tips, interest rates, grades, and statistics. The three most common calculations are finding a percentage of a number, working out what percent one value is of another, and measuring the increase or decrease between two numbers. Each uses a simple formula, but doing them by hand invites mistakes. We built this tool to make those calculations instant and accurate, computed entirely in your browser.
How to Calculate a Percentage
It's simple. Pick the calculation you need. To find a percentage of a number, enter the percent and the value — for example, 20% of 150 gives 30. To find what percent one number is of another, enter both — 30 out of 150 is 20%. To find a percentage change, enter the original and new values to see the increase or decrease. The answer appears instantly as you type. Every calculation happens in your browser, so nothing you enter is sent to a server.
Common Mistakes to Avoid
❌ Confusing "percent of" with "percent change.
✓ Solution:
"20% of 150" and "a 20% increase on 150" are different calculations. The first gives 30; the second gives 180. Make sure you're using the right mode for what you actually need.
❌ Mixing up the two numbers in a change calculation
✓ Solution:
Percentage change is measured from the original value, not the new one. Swapping which number is "original" flips and distorts the result. Always enter the starting value as the original.
❌ Forgetting that percentage increase and decrease aren't symmetric
✓ Solution:
A 50% increase followed by a 50% decrease doesn't return you to the start. Because each percentage is taken from a different base, the two don't cancel out. Calculate each step from its own starting value.
❌ Adding percentages that have different bases
✓ Solution:
You can't simply add a 10% discount and a 10% tax as 20%, because they apply to different amounts. Apply each percentage to its correct base in the right order instead of combining them.
❌ Misplacing the decimal point
✓ Solution:
A percent is a value out of 100, so 5% is 0.05, not 0.5. Slipping a decimal is the most common percentage error. Let the calculator handle the conversion so the decimal stays correct.
Frequently Asked Questions
Multiply the number by the percentage divided by 100. For example, 20% of 150 is 150 × 0.20 = 30. This calculator does it instantly — just enter the percent and the value, and the answer appears right away.
Divide the first number by the second, then multiply by 100. For example, 30 out of 150 is (30 ÷ 150) × 100 = 20%. Enter both numbers in the tool and it returns the percentage automatically.
Subtract the original value from the new value, divide by the original, and multiply by 100. If the result is positive it's an increase; if negative, a decrease. The calculator handles this for you when you enter the original and new numbers.
Because each percentage is calculated from a different starting number. A 50% rise then a 50% fall lands below where you began, since the fall is taken from the larger amount. This is why order and base matter in percentage math.
No. All calculations run locally in your browser — nothing you enter is uploaded, logged, or stored on any server. That makes the tool private and safe to use for any numbers, since your figures never leave your device.
Percentage Calculator — Free Online Tool to Find Percentages, Increases & Decreases Instantly
A percentage calculator that answers the three percentage questions you run into most. First, what is X% of a number — handy for discounts, tips, taxes, and interest. Second, what percentage one number is of another — useful for scores, progress, and proportions. Third, the percentage increase or decrease between two values — perfect for price changes, growth, and comparisons. Just enter your numbers and the answer appears instantly, with clean, accurate results you can rely on. No need to remember formulas or reach for a manual calculation. Whether you're shopping, splitting a bill, checking a grade, or analyzing a change, the tool does the math for you in real time. Because every calculation runs locally in your browser, nothing you enter is uploaded, logged, or stored. It's a fast, private, and free everyday utility for students, shoppers, professionals, and anyone who works with numbers.
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