Percentage Calculator

Calculate percentages instantly. Find what percent one number is of another, calculate percentage increase or decrease, and solve percentage problems.

Percentage (%)

of Number

About Percentage Calculator

How Percentages Work

A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin per centum, meaning "by the hundred." When you say 50%, you mean 50 out of every 100, which is equivalent to the fraction ½ or the decimal 0.5.

Percentage = (Part ÷ Whole) × 100
Part = (Percentage ÷ 100) × Whole
Whole = Part ÷ (Percentage ÷ 100)

These three rearrangements of the same formula let you solve any basic percentage problem. Simply identify which two values you know and solve for the third.

Common Uses of Percentages

Finance: Interest rates, tax calculations, discounts, profit margins, and investment returns are all expressed as percentages.
Statistics: Survey results, probability, and data analysis rely heavily on percentages to communicate proportions clearly.
Science: Concentrations, error margins, and efficiency ratings use percentages to standardize comparisons.
Everyday life: Tips at restaurants, nutritional information on food labels, battery charge levels, and sale prices.

Mental Math Tips for Percentages

10% shortcut: Move the decimal point one place to the left. 10% of 250 = 25.
5% shortcut: Find 10% and halve it. 5% of 250 = 12.5.
25% shortcut: Divide by 4. 25% of 200 = 50.
1% shortcut: Move the decimal two places left. 1% of 350 = 3.5.
Flip trick: X% of Y equals Y% of X. So 8% of 50 is the same as 50% of 8 = 4.

A Brief History of Percentages

The concept of percentages dates back to ancient Rome, where calculations were often made in fractions of 100. Emperor Augustus levied a tax of 1/100 on goods sold at auction, known as centesima rerum venalium. By the 15th century, Italian merchants commonly used "per cento" in commercial arithmetic.

The modern % symbol evolved from abbreviations of "per cento" in handwritten manuscripts. Over centuries, "per cento" was shortened to "p. cento," then "p.c.," and eventually the two circles of the % symbol. Today, percentages are indispensable in fields from finance to science, providing a universal way to compare proportions.

Frequently Asked Questions

What does percent mean?

Percent literally means 'per hundred.' It is a way of expressing a number as a fraction of 100. For example, 45% means 45 out of 100, or 0.45 as a decimal.

How do I convert a percentage to a decimal?

Divide the percentage by 100. For example, 75% becomes 75 ÷ 100 = 0.75. To convert a decimal back to a percentage, multiply by 100.

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, to find what percent 25 is of 200: (25 ÷ 200) × 100 = 12.5%.

What is the difference between percentage change and percentage difference?

Percentage change measures how much a value increased or decreased relative to its original value. Percentage difference compares two values relative to their average and is always positive.

Can a percentage be greater than 100%?

Yes. A percentage greater than 100% means the value exceeds the whole. For example, if a stock price rises from $50 to $150, that is a 200% increase, meaning the new value is 300% of the original.

How do I calculate a percentage increase or decrease?

Use the formula: ((New Value − Old Value) ÷ Old Value) × 100. A positive result indicates an increase, while a negative result indicates a decrease.

Additional Resources

Percentage - Wikipedia Intro to Percentages - Khan Academy Percentages - Math is Fun

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