How do I calculate percentage increase?

Percentage Increase = ((New Value - Original Value) / Original Value) × 100. For example, if a price went from $50 to $65, the increase is ((65-50)/50) × 100 = 30%.

How do I find the original number after a percentage decrease?

Divide the current value by (1 - percentage/100). For example, if something is $80 after a 20% discount, the original was $80 / 0.80 = $100.

What is the difference between percentage and percentile?

Percentage is a proportion out of 100. Percentile indicates the position in a ranked list - the 90th percentile means you scored higher than 90% of participants.

Percentage Calculator

The percentage calculator answers six common percentage questions on one page: what is P% of a number, what percent one number is of another, what whole number

Percentage Calculator Tool

Enter your values in the calculator above, then use the explanations below to understand the result, check assumptions, and compare scenarios.

About this calculator

The percentage calculator answers six common percentage questions on one page: what is P% of a number, what percent one number is of another, what whole number has a given percentage equal to a known part, percentage increase, percentage decrease, and percentage change between two values. Percentages appear in discounts, taxes, grades, financial statements, measurements, statistics, and everyday comparisons. A percentage means a quantity per hundred, so 25% is the same as 25/100 or 0.25. The key is identifying the whole, the part, and the unknown before choosing the relationship.

Use percentage amount = whole × percentage ÷ 100 when the whole and rate are known. Use percentage = part ÷ whole × 100 when the part and whole are known. Use whole = part ÷ (percentage ÷ 100) when the part and percentage are known. For percentage change, use (new − original) ÷ original × 100. Increase and decrease modes apply the selected rate to the starting value and then add or subtract that amount.

A percentage describes a relative relationship rather than an absolute amount. The Solve For modes let you choose which part of the percentage relationship is unknown instead of rearranging the formula manually. For percentage change, the original value is the reference denominator, so reversing a change can produce a different percentage because the reference value changes.

Worked examples

Find 15 percent of 240

You know the whole and percentage and want the percentage amount.

Convert 15% to 0.15
Multiply 240 × 0.15
The result is 36

Result: 15% of 240 is 36.

Find what percent 30 is of 120

You know the part and whole and want the percentage.

Divide the part by the whole: 30 ÷ 120 = 0.25
Multiply by 100
The result is 25%

Result: 30 is 25% of 120.

Find the whole when 30 is 25 percent

You know that a part equals a certain percentage and want to solve for the original whole.

Convert 25% to 0.25
Divide the part by the decimal percentage: 30 ÷ 0.25
The result is 120

Result: If 30 is 25% of a number, the whole is 120.

Find the percentage increase from 80 to 100

A value rises from 80 to 100 and you want the relative increase.

Find the change: 100 − 80 = 20
Divide by the original value: 20 ÷ 80 = 0.25
Multiply by 100 to express the result as a percent

Result: The increase from 80 to 100 is 25%.

Practical tips

Identify which quantity is unknown: the part, percentage, whole, or relative change.
Use What %? when you know the part and whole but need the rate.
Use Find Whole when you know the part and percentage but need the original total.
For percentage change, divide by the original value, not the new value.
Keep extra decimal places until the final step when inputs are not whole numbers.
Distinguish percentage points from percent change when comparing two rates.

Common mistakes

Swapping the part and whole when asking what percent one value is of another.
Dividing by the percentage as a whole number instead of converting it to decimal form when solving for the whole.
Using the new value as the denominator when the question asks for change from the original value.
Treating 15% as 15 instead of 0.15 in multiplication or reverse-percentage formulas.
Confusing a 5 percentage-point increase with a 5% relative increase.
Rounding intermediate values too early and changing the final result.

Percentage calculator modes and formulas

Question	Formula
What is P% of B?	B × P ÷ 100
What percent is A of B?	A ÷ B × 100
A is P% of what number?	A ÷ (P ÷ 100)
Increase B by P%	B × (1 + P ÷ 100)
Decrease B by P%	B × (1 − P ÷ 100)
Percentage change from A to B	(B − A) ÷ A × 100

Frequently asked questions

How do I calculate what percent one number is of another?: Use the What %? mode. Divide the part by the whole and multiply by 100. For example, 30 out of 120 is 25%.
How do I find the original whole from a percentage and a part?: Use Find Whole. Divide the known part by the percentage written as a decimal. If 30 is 25% of the whole, 30 ÷ 0.25 = 120.
Is this a reverse percentage calculator?: Yes. Find Whole reverses the usual percentage-of formula when the result and percentage are known, while What %? solves for the percentage when the part and whole are known.
How is percentage increase different from simply subtracting two values?: Subtraction gives the absolute change, while percentage increase divides that change by the original value and expresses the relationship per hundred.
What is the difference between percent and percentage points?: Percentage points describe the direct difference between two percentages, while percent change measures that difference relative to the starting percentage.
Why can reversing a percentage change produce a different percentage?: The denominator changes because each direction uses a different starting value. Going from 80 to 100 is a 25% increase, while 100 to 80 is a 20% decrease.