Percentage Change Calculator: Increase & Decrease

Work out the percentage change between two numbers, or switch modes to find X% of a number, what percent one number is of another, or increase or decrease a number by a percentage.

Percentage change formula

Percentage change = (New value − Old value) ÷ |Old value| × 100

Example: from 80 to 100 is (100 − 80) ÷ 80 = +25%. From 100 back to 80 is −20%. The two aren’t the same because the starting point changes.

Other percentage formulas

Question	Formula	Example
What is A% of B?	A ÷ 100 × B	15% of 200 = 30
A is what % of B?	A ÷ B × 100	30 of 200 = 15%
Increase B by A%	B × (1 + A/100)	200 + 15% = 230
Decrease B by A%	B × (1 − A/100)	200 − 15% = 170
% difference	\|A − B\| ÷ ((A + B) / 2) × 100	80 vs 100 = 22.22%

Question

Formula

Example

What is A% of B?

A ÷ 100 × B

15% of 200 = 30

A is what % of B?

A ÷ B × 100

30 of 200 = 15%

Increase B by A%

B × (1 + A/100)

200 + 15% = 230

Decrease B by A%

B × (1 − A/100)

200 − 15% = 170

% difference

|A − B| ÷ ((A + B) / 2) × 100

80 vs 100 = 22.22%

Percentage change has a direction (from old to new). Percentage difference compares two values with no starting point, so it uses their average.

Percentages in trading

Gains and losses aren’t symmetrical: after a 50% loss you need a 100% gain to get back to where you started. The drawdown calculator shows this for any loss. For the return on a trade, use the stock profit or ROI calculator.

ChartWatch is independent and not affiliated with TradingView, any broker or exchange. This calculator uses only the numbers you enter and runs in your browser. Results are estimates before taxes and any costs you leave out. It is a calculation tool, not financial advice.

FAQ

How do you calculate percentage change?

Subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 100 is a 25% increase.

How do you calculate a percentage decrease?

Use the same formula. A negative result is a decrease: from 100 to 80 is (80 − 100) ÷ 100 × 100 = −20%.

What is the difference between percentage change and percentage difference?

Percentage change measures a move from an old value to a new one. Percentage difference compares two values without a starting point, dividing by their average.

Why is a 20% drop not undone by a 20% rise?

Because the rise starts from a smaller number. 100 falls 20% to 80, and 80 needs to rise 25% to get back to 100.

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