Percentage Calculator

Every Percentage Question, Answered Instantly

Percentages are the arithmetic of everyday decisions — discounts, taxes, tips, raises, interest, statistics, grades — and yet they reliably produce hesitation, because the same little “%” sign hides three genuinely different questions. This calculator separates them cleanly, so you pick the question you are actually asking and get the answer immediately, with the formula shown so the math is never a black box.

The Three Calculations

1. What is X% of Y? — The direct question: what is 18% of 250? (Answer: 45.) This is the tip on a bill, the tax on a price, the deposit on a purchase. Formula: Y × X ÷ 100.
2. X is what percent of Y? — The reverse: 45 is what percent of 250? (Answer: 18%.) This converts raw numbers into rates: your score out of the maximum, expenses as a share of income, conversions as a share of visitors. Formula: X ÷ Y × 100.
3. Percentage change from X to Y — The trickiest: from 250 to 295 is what change? (Answer: +18%.) Price rises, salary raises, traffic growth, weight loss. Formula: (Y − X) ÷ X × 100 — note the division by the starting value, the detail people misremember.

How to Use It

Choose the tab matching your question, enter the two numbers, and read the result — recalculated live as you type, with the worked formula displayed beneath. No submit buttons, no rounding surprises: results show sensible decimal places and the full-precision value is a copy-click away.

The Mistakes This Tool Quietly Prevents

• Direction confusion in change: a rise from 100 to 150 is +50%, but the fall from 150 back to 100 is −33%, not −50%, because the base changed. The calculator always divides by the value you label as the starting point.
• Stacked percentages: a 20% discount followed by another 20% is not 40% off — it is 36%, because the second discount applies to the already-reduced price. Run the steps separately and the calculator makes the compounding visible.
• Percentage points vs. percent: an interest rate moving from 4% to 5% rose one percentage point, but 25 percent. When precision matters — and with money it does — knowing which number you are quoting prevents expensive misunderstandings.

Quick Mental Anchors Worth Keeping

For everyday estimation: 10% is one decimal shift (10% of 380 is 38); 5% is half of that; 1% is two shifts. Tips, taxes and discounts can be assembled from these pieces — 15% is 10% plus half again. And the elegant symmetry that surprises everyone once: X% of Y always equals Y% of X, so 8% of 50 is the same as 50% of 8 — which is 4, computed instantly. For everything beyond mental range, this calculator is here: free, instant, private (calculations never leave your browser) and accurate to every decimal you need.

One Calculator, Three Daily Moments

To make the three modes concrete: at lunch, mode one computes the 15 percent tip on a 240 bill. In a meeting, mode two turns "38 sign-ups from 510 visitors" into a 7.45 percent conversion rate. Reviewing prices, mode three reveals that the jump from 79 to 94 is an 18.99 percent increase — worth knowing before accepting a renewal. The math is identical each time; choosing the right question is the whole trick, and the tabs make that choice explicit.