Percentage Calculator

To find a percentage of a number, multiply the number by the percentage and divide by 100 — for example, 25% of 200 is 200 × 25 ÷ 100 = 50.

Results are computed from your inputs and rounded for display. Verify important figures independently.

This calculator answers the three questions people actually ask about percentages: what is A% of B, A is what percent of B, and what is the percentage change from A to B. Pick a mode, enter two numbers, and the result appears instantly — nothing is sent to any server.

Formula & methodology

A% of B = A ÷ 100 × B
A as % of B = A ÷ B × 100
Change from A to B = (B − A) ÷ |A| × 100 — the absolute value keeps the direction of change meaningful when starting from a negative number.

Worked examples

25% of 200 → 200 × 0.25 = 50
30 out of 120 → 30 ÷ 120 × 100 = 25%
Price moved from 80 to 100 → (100 − 80) ÷ 80 × 100 = +25% — note the reverse trip from 100 back to 80 is only −20%, because the base changed. This asymmetry is the most common percentage mistake.

Limits

Percentage change from a zero base is undefined — the calculator tells you instead of showing a misleading number.

Frequently asked questions

Why is the % increase and % decrease between the same two numbers different?

Because each direction uses a different base. Going 80→100 divides the 20-unit change by 80 (+25%), while 100→80 divides it by 100 (−20%).

Does this work with negative numbers?

Yes. Percentage change uses the absolute value of the starting number as the base, so a move from −50 to 50 is a +200% change.