How to Calculate Percentage Increase (Formula and Examples)

Percentage increase shows up everywhere, from a pay rise and a price change to your website traffic growing month over month. The good news is that a single formula handles it, and once you know it you can work out any percentage change in a few seconds. This guide walks through the formula, clear examples, and the one mistake that catches most people out.

The percentage increase formula

To find the percentage increase between an old (starting) value and a new value, use this formula:

percentage increase = ((new value - old value) ÷ old value) × 100

In plain words: subtract the old value from the new value, divide by the old value, and multiply by 100. If the answer is positive, the value went up. If it is negative, the value went down, which is a percentage decrease.

How to calculate a percentage increase step by step

1. Subtract the old value from the new value to find the change.
2. Divide that change by the old value.
3. Multiply the result by 100 to turn it into a percentage.

That is the whole method, and it works for any two numbers.

Percentage increase between two numbers: an example

Say your monthly traffic grew from 4,000 to 5,000 visits. To find the percentage increase between these two numbers:

• Change: 5,000 - 4,000 = 1,000
• Divide by the old value: 1,000 ÷ 4,000 = 0.25
• Multiply by 100: 0.25 × 100 = 25% increase

So traffic rose by 25 percent.

Another example: a price rise

Suppose a product went from $80 to $100.

• Change: 100 - 80 = 20
• Divide by the old value: 20 ÷ 80 = 0.25
• Multiply by 100: 25% increase

Notice that a different pair of numbers can give the same percentage. The percentage always describes the change relative to the starting value.

Percentage increase and decrease

The same formula covers a decrease. If the new value is smaller than the old one, the result is simply negative.

Say a subscription dropped from $50 to $40:

• Change: 40 - 50 = -10
• Divide by the old value: -10 ÷ 50 = -0.2
• Multiply by 100: 20% decrease

The negative sign just tells you the value fell. Many people write this as a "20% decrease" and drop the minus sign once the direction is clear.

The mistake to avoid

Always divide by the old value, not the new one. Dividing by the new value is the single most common error, and it gives a different, wrong answer. The old value is your starting point, so it is the baseline you compare against.

A related trap: a 50% drop followed by a 50% rise does not bring you back to the start. If $100 falls by 50% to $50 and then rises by 50%, you reach $75, not $100, because the second percentage is taken from the smaller number.

Do it instantly

If you would rather not do the arithmetic by hand, our free Percentage Calculator works out the percentage increase or decrease between any two numbers as you type, and shows increases in green and decreases in red so the direction is obvious at a glance.

Frequently asked questions

What is the formula for percentage increase? Percentage increase = ((new value - old value) ÷ old value) × 100. Subtract the old value from the new value, divide by the old value, then multiply by 100.

How do you calculate percentage increase between two numbers? Find the difference between the two numbers, divide it by the first (older) number, and multiply by 100. For example, from 4,000 to 5,000 is (1,000 ÷ 4,000) × 100 = 25 percent.

How do you work out a percentage increase quickly? Divide the new value by the old value, subtract 1, then multiply by 100. From 80 to 100 that is (100 ÷ 80) - 1 = 0.25, which is 25 percent. It is the same answer, just fewer steps.

How do you calculate percentage increase and decrease? Use the same formula for both. A positive result is an increase and a negative result is a decrease. The size of the number is the percentage, and the sign is the direction.

The takeaway

Subtract the old value from the new value, divide by the old value, and multiply by 100. A positive answer is an increase and a negative answer is a decrease. Divide by the starting number every time and you will get percentage change right, whether you are working it out by hand or checking it with a calculator.