Percentage Calculator

What is Percentage Calculator?

The Percentage Calculator helps you quickly solve common percentage questions - like finding a percent of a number, converting a ratio to a percent, and measuring percent change.

It’s useful for shopping discounts, comparing growth or decline, budgeting, grades, analytics, and any everyday math where “percent” is involved.

What it can calculate

What is P% of X? - calculates a percentage of a value.

X is what percent of Y? - converts X/Y into a percentage.

Percent change from A to B - shows how much something increased or decreased.

Increase / decrease X by P% - applies a percent adjustment to a value.

Notes & tips

If a result looks too large or small, double‑check that you entered the percent as a number (e.g., 15 for 15%, not 0.15).

For percent change, the starting value (A) cannot be 0.

Use commas if you want-inputs accept them and calculations still work.

FAQ

Do I enter 15% as 15 or 0.15?

Enter 15 for 15%. If you enter 0.15, the calculator treats it as 0.15%.

If your data is in decimal form (0.15 = 15%), multiply by 100 before entering it.

How is “X is what percent of Y?” calculated?

It uses: (X ÷ Y) × 100. Example: 25 is what percent of 200? → (25 ÷ 200) × 100 = 12.5%.

If Y = 0, the result is undefined, so the calculator leaves it blank.

What’s the difference between percent change and percent difference?

Percent change compares a new value to a starting value: (B − A) ÷ A × 100.

Percent difference is a symmetric comparison that uses the average of A and B (often used in science). This tool shows percent change.

Why can’t percent change start from 0?

Percent change divides by the starting value (A). If A = 0, you’d be dividing by zero, which is undefined.

In that case, use an absolute change (B − A) or compare against a non‑zero baseline.

How does “increase / decrease by P%” work?

Increase uses: X × (1 + P/100). Decrease uses: X × (1 − P/100).

Example: decrease 80 by 25% → 80 × 0.75 = 60.

Can results be negative?

Yes. If you enter negative numbers, the math follows standard rules. For example, a change from −50 to −25 is a +50% change (because the value became “less negative”).

How does rounding work?

Results are displayed with a reasonable number of decimals depending on size. For money, you can treat the displayed value as an estimate and round to your currency’s smallest unit (like cents).

How do I convert a fraction or “X out of Y” into a percent?

Use the “X is what percent of Y?” row. Example: 3 out of 8 → enter X=3, Y=8 → 37.5%.