Percentage Calculator

What this calculator does

A percentage calculator answers one of three everyday questions. The first is “what is X percent of Y”: fifteen percent of eighty is twelve. The second is “X is what percent of Y”: twelve is twenty percent of sixty. The third is the change from a starting value A to an ending value B, written as a percent of A. Those are different jobs. Mixing them in one unlabeled box is how people get a result that looks precise and is the wrong question.

This percentage calculator keeps the three modes visible. You pick the question, enter the two numbers, and read a labeled result. Empty fields, non-numeric text, and division by zero are rejected in the status line. The page does not print Infinity or NaN. Nothing is uploaded. The arithmetic runs in this browser with the numbers you typed.

Use this page for school work, a quick check of a claim, or a sanity check before you open a spreadsheet. Do not treat it as a financial calculator, a tax engine, or a statistical package. It does not know currency, compounding, or samples. If your job is “how much did this value move,” the dedicated Percentage Change Calculator states increase, decrease, or unchanged. If your job is a sale price, use the Discount Calculator.

How to use

1. Choose the calculation. The field labels change so X and Y mean the right thing.
2. Enter the two numbers. Commas in thousands are stripped. Scientific notation is accepted when it is a real number.
3. Calculate. The result is labeled. Example fills a known pair. Clear empties the fields.

Keyboard users can move between fields and press Enter to calculate. Each field has a visible label. Focus uses the same outline as the other YallaSolve tools.

Formula

What is X% of Y: result = (X ÷ 100) × Y. X is what percent of Y: result = (X ÷ Y) × 100, and Y must not be 0. Percentage change from A to B: result = ((B − A) ÷ A) × 100, and A must not be 0. Those identities are ordinary school arithmetic. The tool does not invent a fourth formula for “percent more than” wording; if you need the signed change with a direction word, switch to the change calculator.

Example

Mode one with X = 15 and Y = 80 returns 12, because 0.15 × 80 = 12. Mode two with X = 12 and Y = 60 returns 20%. Mode three with A = 40 and B = 50 returns 25%, an increase of ten on a base of forty. If you set Y or A to 0 in a mode that divides by that value, the status explains the block instead of drawing a fake percentage.

15% of 80 = 12
12 is 20% of 60
40 → 50 is +25%

Limits

• An original or whole value of 0 cannot produce a percentage. The status says so.
• Negative numbers are allowed and follow the same algebra. A negative base with a positive new value is a decrease through zero, which can look surprising; read the sign.
• Results are ordinary floating-point numbers, then trimmed for display. This is not arbitrary-precision decimal math.
• The page does not convert units, apply tax, or decide whether a business “increased prices by 10%.”

If you already know you want only the signed change between two amounts, skip the extra modes and open the Percentage Change Calculator. For a marked-down price, the Discount Calculator shows the amount off and the final price.