Percentage Calculator
Calculate percentages instantly. Six common percentage formulas, all in one place with real-time results.
Free Online Percentage Calculator
The SmarterSources Percentage Calculator provides six essential percentage calculations in one convenient tool. Whether you need to find what percentage one number is of another, calculate a percentage increase or decrease, or determine the percentage change between two values, this calculator delivers instant, accurate results as you type.
How to Calculate Percentages
A percentage represents a fraction of 100. The word "percent" literally means "per hundred." To find a percentage of a number, multiply the number by the percentage and divide by 100. For example, 20% of 150 is (150 x 20) / 100 = 30. This fundamental formula underpins all six calculators on this page.
Understanding Percentage Change
Percentage change measures the relative difference between an old value and a new value. The formula is: ((New Value - Old Value) / |Old Value|) x 100. A positive result indicates an increase, while a negative result indicates a decrease. This calculation is commonly used in finance, business reporting, and data analysis to express how much something has grown or declined.
Percentage Increase vs. Percentage Decrease
A percentage increase adds a proportion to the original value: New Value = Original + (Original x Percentage / 100). A percentage decrease subtracts it: New Value = Original - (Original x Percentage / 100). These are commonly used in pricing, salary adjustments, and statistical analysis. Note that a 50% increase followed by a 50% decrease does not return you to the original value.
Common Percentage Conversions
To convert a fraction to a percentage, divide the numerator by the denominator and multiply by 100. For example, 3/4 = 0.75 = 75%. To convert a decimal to a percentage, simply multiply by 100. To convert a percentage to a decimal, divide by 100. These conversions are fundamental to working with percentages in any context.
Frequently Asked Questions
How do you calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 200 is (200 x 15) / 100 = 30. You can also convert the percentage to a decimal first: 15% = 0.15, then 200 x 0.15 = 30.
How do you calculate percentage change?
Use the formula: ((New Value - Old Value) / |Old Value|) x 100. For example, the percentage change from 80 to 100 is ((100 - 80) / 80) x 100 = 25% increase. From 100 to 80 it would be ((80 - 100) / 100) x 100 = -20% decrease.
What is the difference between percentage change and percentage point change?
Percentage change is relative to the original value, while percentage point change is an absolute difference. If a rate goes from 5% to 8%, that is a 3 percentage point increase but a 60% percentage change ((8-5)/5 x 100). These are very different measures and are often confused in everyday communication.
Why does a 50% increase then 50% decrease not return to the original?
Because the decrease is applied to the larger, increased value. If you start with 100, a 50% increase gives you 150. A 50% decrease of 150 gives you 75, not 100. The base changes between the two operations, which is why the result differs.
How do you reverse a percentage?
To find the original value before a percentage was applied, use the "X is Y% of what?" formula: Original = Current Value / (Percentage / 100). For example, if 30 is 15% of an unknown number, the original is 30 / 0.15 = 200.
Is my data safe with this calculator?
Yes. All calculations run entirely in your browser. No data is sent to any server, and nothing is stored. Your numbers remain completely private.