Percentage Calculator
Find percentages, ratios and percent change instantly.
How to use
- Choose the mode you need at the top: what is X% of Y, X as a percentage of Y, or percent change from X to Y.
- Enter the two values for the current mode: results update in real time as you type, with no button to press.
- Each result is shown in its own card; click "Copy result" to copy the full set of numbers for the current mode.
- Each mode keeps its own inputs, so you can switch back and forth to compare results.
FAQ
What does "what is X% of Y" mean?
How is "X as a percentage of Y" calculated?
What is the difference between percent change and a ratio?
How many decimal places do results keep?
Screenshots
How to use
- Pick a calculation mode
Three radio options sit at the top. They are what is X% of Y, X is what percent of Y, and percent change from X to Y. Only the two fields that mode needs stay visible.
- Enter the two values
Fill both fields with the hints in mind: X = 15 for 15% and Y = 200 in mode one. Results update as you type, and there is no button to press.
- Read the result cards
Each card shows the main value, the remainder (Y minus the result) and the formula used. For example 15% × 200 = 30, with 170 left, so the math is easy to check.
- Copy or compare
Click Copy result to capture every figure in the current mode. Each mode remembers its own inputs, so switch back and forth to compare results side by side.
- Mind the base value
In mode two the total Y cannot be 0, and in mode three the starting value X cannot be 0. Invalid input shows a red error notice instead of a number.
About this tool
This percentage calculator covers the three everyday percent problems. It handles a percentage of a number, one number as a share of another, and the change between two values. It applies Y × X ÷ 100, X ÷ Y × 100 and (Y - X) ÷ X × 100. The formula used is printed beside each result. Plain numbers keep up to six decimals and percentages keep four.
Use it for retail math, budgets and quick analysis. A 320 item at 25% off is mode one with X = 25. If 30 of 200 survey answers were yes, mode two returns 15%. A salary moving from 8,000 to 9,200 is mode three at +15%. The remainder of a mode-one calculation is printed under the main result. That answers reverse questions too, such as what is left after the discount.
How it works
The percent sign descends from per cento, a phrase Italian merchants wrote in their ledgers in the 15th century. The abbreviation passed through forms like per c° before settling into the modern % in the 18th century. A percentage is just a fraction with a fixed denominator of 100, and it carries no direction on its own. A rate moving from 3% to 5% is up 2 percentage points, and up about 66.7% relative to the start. Both statements are correct: the first is a difference of two rates, the second divides by the starting value. Financial writing mixes the two often. State the base whenever you quote a change.
Percent change always divides by the starting value. A price moving from 100 to 125 gains 25%. Falling back from 125 to 100 shows a 20% drop, because the denominator is now 125. Consecutive changes multiply: (1+25%)×(1-20%) equals 1, and the price lands back where it began. Stacked discounts work the same way. Two 25%-off passes leave 0.75² = 56.25% of the original price, not half. Only rates measured from the same base can be added or subtracted. When you quote a change, name the base in the sentence, such as last month or last year, and the number stops being ambiguous.
When to use it
- Checking a sale price
When a discount stacks with a coupon, compute the discounted price in mode one. Feed the final amount paid through mode two to recover the real discount rate, and fake markdowns show themselves immediately.
- Reporting consistent figures
A cost falling from 800,000 to 680,000 is a 15% drop. Paste the formula alongside the number so readers know the base is the original value. The drop then can never be mistaken for a share.
- Class and survey statistics
With 45 passes among 60 students, mode two returns a 75% pass rate. Tracking that share across quizzes compares fairly where raw scores do not. Group size stops distorting the picture.
Tips & tricks
- In percent-change mode a positive result means growth and a negative one a decline. A starting value of 0 cannot be used.
- For stacked discounts run mode one twice: compute the first discounted price, then feed it back in as Y for the second percentage.
- Mode two is a share finder, handy for pass rates, completion rates and cost breakdowns in reports.
Things to watch
- Reversed bases flip conclusions
A being 25% more than B and B being 20% less than A describe one pair of numbers. State what each figure is measured against, or the same data will support opposite stories.
- Percent versus percentage points
A tax moving from 8% to 10% rises 2 percentage points, or 25% relatively. The gap in stated impact is an order of magnitude. Rates, fees and taxes deserve the distinction every time they are quoted.
- Never round between steps
Rounding every intermediate result to two decimals while chaining discounts, taxes and commissions drifts the total by cents or more. Carry full precision through the chain. Round only the final figure you actually pay.