Planos

Calculadora de porcentagem

Calcule qualquer porcentagem em segundos — por exemplo, 37 de 40 em porcentagem é 92.5%. Escolha o que quer encontrar, digite dois números e clique em Calcular para ver a resolução.

Resultado

Digite os valores e toque em Calcular para ver o resultado.

Fórmula

X% of Y=X100×YX\% \text{ of } Y = \frac{X}{100} \times Y

A percentage is a number of hundredths, so X% means X ÷ 100.

percent=partwhole×100%\text{percent} = \frac{\text{part}}{\text{whole}} \times 100\%

Divide the part by the whole, then multiply by 100.

change=new−original∣original∣×100%\text{change} = \frac{\text{new} - \text{original}}{|\text{original}|} \times 100\%

A positive result is an increase and a negative result is a decrease, measured relative to the original value.

Como usar esta calculadora

  1. Choose the question you want to answer.
  2. Enter the two numbers. Decimals such as 12.5 and negative values are allowed.
  3. Press Calculate. Changing an input afterwards marks the result as outdated until you calculate again.
  4. If a result had to be rounded, it is labelled approximate and the exact fraction is shown too.

Exemplos resolvidos

Easy: 20% of 200,000

Choose “What is X% of Y?”, enter 20 and 200000.

20% means 20 hundredths: 20 ÷ 100 = 0.2.

Multiply by 200,000: 0.2 × 200,000 = 40,000.

Check: 40,000 ÷ 200,000 = 0.2, which is 20%. So 20% of 200,000 (200k) is 40,000.

Medium: 37 out of 40 as a percentage

Choose “X is what percent of Y?”, enter 37 as the part and 40 as the whole.

Divide the part by the whole: 37 ÷ 40 = 0.925.

Multiply by 100 to turn the decimal into a percentage: 0.925 × 100 = 92.5%.

Check: 92.5% of 40 is 0.925 × 40 = 37. So a test score of 37/40 is 92.5%.

Hard: 6 out of 21 as a percentage

Simplify first if you can: 6/21 = 2/7, because 6 and 21 are both divisible by 3.

2 ÷ 7 = 0.285714… — the digits 285714 repeat forever, so the answer has to be rounded.

Multiply by 100: 28.571428…%, which is 28.57% to two decimal places. Sumzo marks the result as approximate and also shows the exact value, 200/7 %.

Check: 0.2857142… × 21 = 6.

Erros comuns

  • Dividing the wrong way round. For “37 out of 40” divide 37 by 40, not 40 by 37 — the second gives about 108%, more than the whole.
  • Forgetting to multiply by 100. 37 ÷ 40 = 0.925 is a decimal; as a percentage it is 92.5%, not 0.925%.
  • Measuring percentage change from the wrong value. Always divide the difference by the original (starting) value, not the new one.
  • Rounding too early. Rounding 6 ÷ 21 to 0.29 before multiplying gives 29% instead of 28.57%. Round only at the end.

Perguntas frequentes

What is 37/40 as a percentage?

92.5%. Divide 37 by 40 to get 0.925, then multiply by 100. So 37 out of 40 on a maths test is 92.5%.

What is 28/40 or 14/20 as a percentage?

Both are 70%. 28/40 and 14/20 both simplify to 7/10, and 7 ÷ 10 = 0.7 = 70%. That also answers “what percent of 20 is 14?”: 70%.

How do I turn a fraction like 9/40 or 7/15 into a decimal?

Divide the top by the bottom. 9 ÷ 40 = 0.225 exactly (22.5%). 7 ÷ 15 = 0.4666…, where the 6 repeats forever, so as a percent 7/15 is 46.67% to two decimal places.

Is percentage change the same as percentage points?

No. Going from 10% to 15% is a change of 5 percentage points, but a 50% increase relative to the original 10%. This calculator gives the relative change.

Why can’t I calculate a change from 0?

Percentage change divides by the original value. When the original value is 0 the division is undefined, so no percentage can be given — Sumzo tells you this instead of showing a misleading number.

Does an increase of 20% followed by a decrease of 20% bring me back to the start?

No. 100 increased by 20% is 120, and 120 decreased by 20% is 96. Each percentage is measured from a different starting value.

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