Math Calculators

Free Percentage Increase/Decrease Calculator Online

Use this free percentage change calculator to find the percent increase or decrease between two numbers, or to increase or decrease a value by a specific percentage. Switch between modes to match what you need - a percentage increase calculator, a percentage decrease calculator, or a straightforward percent difference calculator - all in one tool.

Old value

New value

Percentage change

Difference

Direction

Starting value

Increase by (%)

New value

Amount added

Starting value

Decrease by (%)

New value

Amount subtracted

What is percentage increase and decrease, and why it matters

A percentage change describes how much a number has grown or shrunk relative to its starting value, expressed as a percentage rather than a raw difference. This matters because a raw difference alone can be misleading - going from 10 to 20 and going from 1,000 to 1,010 are both a difference of 10, but one is a 100% increase and the other is barely a 1% increase. Percentage change is used constantly in everyday and professional contexts: tracking a price increase, comparing sales growth between two periods, understanding a pay raise, or figuring out how much a discount actually saves you. Knowing the correct formula - and which number is the "starting" value - avoids a common mistake where people accidentally calculate the percentage relative to the wrong number. Getting this backwards is one of the most frequent small errors in everyday percentage math, and it produces a plausible-looking but incorrect answer rather than an obvious one.

How this calculator works

For percentage change between two numbers, this tool uses the formula ((new value - old value) / old value) x 100, which always measures the change relative to the original starting value, not the new one. A positive result is shown as an increase and a negative result as a decrease. For the increase and decrease modes, the calculator works in the opposite direction: it multiplies your starting value by (1 + percentage/100) to increase it, or by (1 - percentage/100) to decrease it, giving you the resulting new value directly. All three modes run instantly in your browser as you type, with no page reload and nothing sent to a server.

Common searches this calculator answers

What is the percentage increase or decrease between two numbers?
How do I calculate a percentage increase on a value?
How do I calculate a discount or percentage decrease?
What is the formula for percentage change?
How much did a price, salary, or sales figure change in percentage terms?
How do I find the percent difference between an old and new number?

How to use it

Choose the mode that matches your question - "Find % change," "Increase by %," or "Decrease by %."
For percentage change, enter the old value and the new value.
For increase or decrease mode, enter your starting value and the percentage to apply.
Read the result instantly - the tool updates as you type.
Switch modes at any time without losing your other entries.

Tips

Always use the original, earlier number as the "old value" - percentage change is measured relative to where you started, not where you ended up.
A percentage increase followed by the same percentage decrease does not return you to the original number - work out both steps separately rather than assuming they cancel out.
For discounts, use the decrease mode directly with the discount percentage rather than calculating the discount amount by hand first.
If your old value is zero, percentage change cannot be calculated, since you cannot divide by zero - use the raw difference instead in that case.
Negative percentages in the change mode simply mean a decrease - the size of the number still tells you the magnitude of the change.

Frequently asked questions

Is this percentage increase/decrease calculator free to use?

Yes. It is completely free, works in your browser, and does not require any sign-up or download.

What is the formula for percentage increase or decrease?

The formula is ((new value - old value) / old value) x 100. A positive result is a percentage increase, and a negative result is a percentage decrease.

What happens if the old value is zero?

Percentage change cannot be mathematically calculated when the old value is zero, since it would require dividing by zero. In that case, consider using the raw numeric difference instead of a percentage.

Does increasing a number by a percentage and then decreasing it by the same percentage return the original number?

No. Because each percentage is calculated relative to a different starting value, increasing then decreasing by the same percentage results in a slightly lower number than you started with. Use the increase and decrease modes separately to see this for yourself.

Can I use this to calculate a discount?

Yes. Use the "Decrease by %" mode, enter the original price as the starting value and the discount percentage, and the result will show the discounted price along with the amount saved.

Can I use this for a salary raise or price increase?

Yes. Use the "Increase by %" mode with your current salary or price as the starting value and the raise or increase percentage to see the new amount and how much was added.

Why does my result show a negative percentage?

A negative percentage in the "Find % change" mode simply indicates a decrease from the old value to the new value. The number itself shows the size of that decrease.

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