How to Calculate Percentage Increase & Decrease (Formula)

To calculate a percentage increase, subtract the old value from the new one, divide by the old value, and multiply by 100:

Percentage change = (new − old) ÷ old × 100

If the answer is positive it is an increase; if it is negative it is a decrease. For example, a salary going from ₹45,000 to ₹50,400 is a (5,400 ÷ 45,000) × 100 = 12% increase. The third row of our percentage calculator ("% change from … to …") does this instantly.

The percent change formula, step by step

Find the difference: new value − old value.
Divide by the old value (the starting point, not the new one).
Multiply by 100 to turn it into a percentage.

The single most common mistake is dividing by the new value. Always divide by where you started.

How to calculate percentage increase: examples

Salary hike percentage

Old monthly salary ₹45,000, new salary ₹50,400.

Difference = 50,400 − 45,000 = 5,400
5,400 ÷ 45,000 = 0.12
0.12 × 100 = 12% hike

The same works for annual CTC. Just do not mix monthly in-hand pay with annual CTC, or with a figure that includes a one-time bonus. Compare the same kind of number before and after.

Price increase

A cooking gas cylinder goes from ₹850 to ₹903.

Difference = 53
53 ÷ 850 × 100 = about 6.24% increase

Increase of more than 100%

Followers grow from 400 to 1,000.

Difference = 600
600 ÷ 400 × 100 = 150% increase

"Up 150%" means 2.5 times the original. Doubling is a 100% increase, not 200%.

How to calculate percentage decrease

The formula is the same; the result comes out negative. Many people prefer to write it the other way round so the answer is positive:

Percentage decrease = (old − new) ÷ old × 100

Example: price drop

A phone drops from ₹80,000 to ₹60,000.

Difference = 20,000
20,000 ÷ 80,000 × 100 = 25% decrease

For a sale price, that 25% is the discount. The discount calculator works the other way: enter the original price and the % off to see what you pay. Our guide on how to calculate discount percentage covers shop offers in more detail.

Example: weight loss

Weight falls from 84 kg to 78 kg.

Difference = 6
6 ÷ 84 × 100 = about 7.14% decrease

Finding the new value from a percentage

Sometimes you know the percentage and want the result.

After an increase: new = old × (1 + percent ÷ 100). A ₹45,000 salary with a 12% hike becomes 45,000 × 1.12 = ₹50,400.
After a decrease: new = old × (1 − percent ÷ 100). An ₹80,000 phone with 25% off becomes 80,000 × 0.75 = ₹60,000.

Reverse percentage: finding the original value

If you only know the value after the change, divide, do not subtract.

Original before an increase = new ÷ (1 + percent ÷ 100). If your salary after a 12% hike is ₹56,000, your old salary was 56,000 ÷ 1.12 = ₹50,000, not 56,000 − 12% (which gives ₹49,280).
Original before a decrease = new ÷ (1 − percent ÷ 100). If a sale price after 20% off is ₹1,600, the original was 1,600 ÷ 0.8 = ₹2,000.

This is the same idea used to remove GST from an inclusive price: the GST calculator divides by (1 + rate ÷ 100) for you.

Why up 20% then down 20% does not cancel out

Start at 100.

Up 20%: 100 × 1.2 = 120
Down 20%: 120 × 0.8 = 96

You end 4% lower, because the second 20% is taken on 120, not 100. To get back from 96 to 100 you need an increase of about 4.17%. More generally, after a fall of x%, you need a rise of more than x% to recover. A 50% fall needs a 100% rise to get back to the start.

To combine two changes, multiply the factors: a 10% rise followed by a 5% rise is 1.10 × 1.05 = 1.155, a 15.5% total rise, not 15%.

Percent vs percentage points

When the thing that changes is itself a percentage, be careful.

If a loan rate goes from 8% to 10%:

It rose by 2 percentage points (10 − 8).
It rose by 25 percent ((10 − 8) ÷ 8 × 100).

Both are correct, but they mean different things. News reports and bank notices usually talk in percentage points, or in "basis points", where 100 basis points = 1 percentage point.

Percentage formula in Excel

With the old value in A2 and the new value in B2:

=(B2-A2)/A2

Then format the cell as a percentage (Home > Number > %). Excel multiplies by 100 for display, so do not multiply by 100 in the formula as well, or you will see 1200% instead of 12%.

Other useful versions:

Increase a value by a percentage (rate in C2, typed as 12%): =A2*(1+C2)
Decrease a value by a percentage: =A2*(1-C2)
Original value before an increase: =B2/(1+C2)
Avoid errors when the old value is zero: =IF(A2=0,"n/a",(B2-A2)/A2)

The same formulas work in Google Sheets.

Common mistakes

Dividing by the new value. Always divide by the old (starting) value.
Subtracting a percentage to reverse it. To undo a 12% increase, divide by 1.12.
Adding successive percentages. Two 10% rises are 21%, not 20%. Multiply the factors.
Mixing percent and percentage points. A move from 8% to 10% is 2 points but a 25% rise.
Multiplying by 100 in Excel and also using % format. Use one or the other.
Comparing different kinds of numbers. Monthly vs annual, gross vs in-hand, with bonus vs without.

For any quick check, the percentage calculator has three rows: X% of a number, what percent one number is of another, and percentage change. If you are working out marks rather than changes, see how to calculate percentage of marks.

Questions

How do I calculate percentage increase?

Subtract the old value from the new value, divide by the old value and multiply by 100. From 45,000 to 50,400: (50,400 − 45,000) ÷ 45,000 × 100 = 12%.

How do I calculate my salary hike percentage?

Take the increase in salary, divide it by your old salary and multiply by 100. Compare like with like: monthly with monthly, or annual CTC with annual CTC.

What is the percentage change formula in Excel?

With the old value in A2 and the new value in B2, use =(B2-A2)/A2 and format the cell as a percentage. A negative result is a decrease.

If something goes up 20% and then down 20%, is it back to the start?

No. 100 up 20% is 120, and 120 down 20% is 96, a net fall of 4%. The second percentage is taken on a bigger base.