Percentages show up everywhere — discounts, grades, tax, tips, statistics — yet the three basic percentage questions are surprisingly easy to mix up. This calculator answers all three at once from just two numbers: what is A% of B, what percentage of B is A, and what is the percent change from A to B.
Cómo funciona
Enter any two values. The calculator computes all three relationships simultaneously so you never have to remember which formula fits your question — just read the line that matches what you asked.
La fórmula
The first formula scales B by the percentage A. The second expresses A as a share of B. The third measures relative growth or decline from A to B.
Ejemplo resuelto
With A = 25 and B = 200: 25% of 200 is 50; 25 is 12.5% of 200; and going from 25 to 200 is a 700% increase. Three different questions, three different answers, from the same two numbers.
Preguntas frecuentes
Why is a 50% increase not undone by a 50% decrease?
Because the second percentage applies to a new, larger base. 100 increased by 50% is 150; decreasing 150 by 50% gives 75, not 100. Percentage changes are relative to their starting point.
What is the difference between percentage points and percent?
Going from 10% to 15% is a rise of 5 percentage points, but a 50% relative increase. News reports often confuse the two — knowing the difference protects you from misleading statistics.
How do I calculate a reverse percentage?
If a price after a 20% discount is 80, the original was 80 ÷ (1 − 0.20) = 100. Divide by (1 ± rate), don't multiply — a common trap.