Percentage Calculator
Calculate ratios, percentages, and percentage changes all in one place. Instantly find discount amounts, proportions, and growth rates for free.
B% of A
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Formula Reference
B% of A — A x B / 100. Example: 20% of 50,000 = 10,000
A is what % of B — (A / B) x 100. Example: 30 is 20% of 150
Percentage Change — (New - Old) / |Old| x 100. Example: 200 to 250 = +25%
Shopping discounts, salary raises, investment returns, exam score ratios — percentage calculations come up constantly in everyday life. Yet recalling the right formula each time can be tedious and error-prone. This percentage calculator combines three essential calculation modes into a single tool, showing results in real time the moment you type a number.
Three Calculation Modes
Mode 1: What is B% of A?
The most common percentage calculation. Find out the discount amount on a $500 item at 20% off, or the 3.5% raise on a $3,000 salary. The formula is A x B / 100. Simply enter the base value and the percentage, and the result appears instantly.
Mode 2: A is What % of B?
Determine what proportion a part represents of the whole. Scored 30 out of 150 on a test? Need to know what share of your budget you have spent? Enter the part and the whole, and the percentage is calculated automatically using (A / B) x 100.
Mode 3: Percentage Change
Enter an old value and a new value to find the rate of change. Track month-over-month revenue growth, year-over-year performance, or investment gains. The formula is (New - Old) / |Old| x 100. Increases appear in green and decreases in red for instant visual clarity.
How to Use
Step 1: Select a Calculation Mode
Click one of the tabs at the top of the tool: "What is B% of A?", "A is what % of B?", or "Percentage Change".
Step 2: Enter Your Values
Type numbers into the input fields for your selected mode. Results are computed in real time — no need to click a separate calculate button.
Step 3: Read the Result
The answer appears immediately below the inputs. In percentage change mode, the result is color-coded green for increases and red for decreases.
Practical Tips
Shopping Discount Amounts
An $890 item is 30% off? Use Mode 1 — enter 890 and 30 to get $267 off instantly. The final price is $890 - $267 = $623.
Salary Raise Verification
Your salary went from $3,000 to $3,150? Use Mode 3 — enter 3000 as the old value and 3150 as the new value to confirm a 5% raise.
Investment Return Calculation
Invested $10,000 and it grew to $12,000? Mode 3 shows a 20% return highlighted in green. Quick and clear for portfolio reviews.
Frequently Asked Questions
What types of calculations can this percentage calculator perform?
It supports three modes: what is B% of A (ratio calculation), A is what percent of B (percentage calculation), and percentage change between an old value and a new value.
How many decimal places are shown in results?
Results are displayed up to two decimal places. If the result is a whole number, it is shown without decimals.
Can I use this on mobile?
Yes, it is fully responsive and works identically on smartphone and tablet browsers.
How is a negative percentage change displayed?
A decrease is shown in red, while an increase is shown in green, making it easy to distinguish at a glance.