How do I calculate a percentage increase?

Subtract the original value from the new value, divide by the original value, then multiply by 100. The percentage-increase mode of this calculator does this automatically — just enter the original and new numbers.

What is the formula for 'X is what percent of Y'?

Divide X by Y and multiply by 100: (X ÷ Y) × 100. For example, 40 is what percent of 160? (40 ÷ 160) × 100 = 25%.

Can this calculator handle negative percentage changes?

Yes. If the new value is smaller than the original, the increase/decrease mode returns a negative percentage, clearly indicating a decrease.

Is a percentage the same as a percentage point?

No — a percentage change is relative (e.g., a rate going from 10% to 15% is a 50% relative increase), while a percentage point change is absolute (a 5-point increase). This tool calculates relative percentage change.

Percentage Calculator

Calculate percentages, percentage increase/decrease, and what percent one number is of another.

Percent

% of

Number

15% of 200 is

How to use the Percentage Calculator

Pick the kind of question you're answering: "% of a number", "X is what % of Y", or "% increase / decrease".
Fill in the two numbers you already know — for a change, put the starting figure in Original value and the later one in New value.
Read the answer underneath. A percentage change is labeled as an increase or a decrease so the direction is never ambiguous.

About the Percentage Calculator

A percentage calculator solves the three most common percentage problems: finding what a percentage of a number is (what is 15% of 200?), finding what percent one number is of another (40 is what percent of 160?), and finding the percentage change between two numbers (increase or decrease). Instead of rearranging the percentage formula by hand, you enter the numbers you know and the tool fills in the rest.

It's built for everyday situations — working out a restaurant tip, a discount at checkout, a grade on a test, or how much a salary or investment has grown or shrunk over time — where speed and accuracy matter more than showing your work.

Worked example

Example: a $80 jacket is on sale for $60. Using the percentage-decrease mode, enter 80 as the original value and 60 as the new value — the tool returns a 25% decrease, which is the discount rate applied at checkout.

The three formulas behind the modes

Every mode is a rearrangement of one relationship: part = whole × percent ÷ 100. '15% of 200' multiplies (200 × 15 ÷ 100 = 30). '40 is what percent of 160' divides (40 ÷ 160 × 100 = 25%). The change mode measures the difference against the starting value: (new − original) ÷ original × 100.

A handy shortcut for mental math: percentages are reversible. 8% of 50 is the same as 50% of 8, which is obviously 4. And 10% of anything is just the number with the decimal point moved one place left, which makes 5%, 15%, and 20% easy to build from it.

Mistakes that give the wrong answer

Undoing a change with the same percentage. A price that rises 25% and then falls 25% doesn't return to where it started: 100 becomes 125, then 93.75, because the second 25% is taken from a larger number.
Mixing up the base. Going from 60 to 80 is a 33.3% increase, but going from 80 back to 60 is a 25% decrease. The base is always the value you start from.
Removing a percentage by subtracting it. To find a price before a 20% markup, divide by 1.2 instead of subtracting 20%: 120 ÷ 1.2 = 100, while 120 − 20% gives 96.
Dividing by zero. A change from 0 has no percentage (any increase from nothing is infinite), so the calculator shows no result when the original value is 0.

Reading percentages in the news

A risk that rises from 1 in 10,000 to 2 in 10,000 is a '100% increase', which sounds alarming but is an absolute change of one hundredth of a percentage point. When a headline quotes a relative change, look for the starting figure before deciding how much it matters.

Frequently asked questions

How do I calculate a percentage increase?: Subtract the original value from the new value, divide by the original value, then multiply by 100. The percentage-increase mode of this calculator does this automatically — just enter the original and new numbers.
What is the formula for 'X is what percent of Y'?: Divide X by Y and multiply by 100: (X ÷ Y) × 100. For example, 40 is what percent of 160? (40 ÷ 160) × 100 = 25%.
Can this calculator handle negative percentage changes?: Yes. If the new value is smaller than the original, the increase/decrease mode returns a negative percentage, clearly indicating a decrease.
Is a percentage the same as a percentage point?: No — a percentage change is relative (e.g., a rate going from 10% to 15% is a 50% relative increase), while a percentage point change is absolute (a 5-point increase). This tool calculates relative percentage change.