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How to Calculate Percentage Decrease

Jen Morris

Published 10 September 2021 · Updated 3 August 2026

The percentage decrease formula is: percentage decrease = (decrease ÷ original value) x 100. Subtract the new value from the original value to find the decrease, divide it by the original value, then multiply by 100. For example, a fall from 16 to 12 is a decrease of 4, and 4 ÷ 16 x 100 = 25, so a 25% decrease.

Where you’ll need it

Percentage decrease questions are a staple of numerical reasoning tests. Employers use them to check you can compare two figures taken from a table or chart, typically values falling between two periods: revenue, costs, headcount, or a total liability dropping from one year to the next.

The same formula covers everyday uses too. If an asset is worth £30,000 in one year and £24,000 the next, the formula expresses that depreciation in percentage terms. You could equally use it to work out a reduction in your energy consumption between two months.

A step-by-step guide to calculating percentage decrease

Whatever the purpose, the method of calculating percentage decrease is the same. It’s a relatively straightforward process that takes just four steps to complete.

Each of these steps is explained below, followed by some practice questions in the style of a numerical reasoning test.

Step 1: Calculate the difference

The first step is to work out the difference, or decrease, between the two figures you’re dealing with. Take the original number, and subtract the new number from it.

As a basic example, say we want to calculate the percentage decrease between 16 and 12. So 16 is our original number, and 12 our new number:

16 - 12 = 4

4 is the numerical value we need to move onto the next step.

Step 2: Divide the decrease by the original number

Next, take the numerical decrease, and divide it by the total value of your original number.

In our basic example, this means dividing 4 by 16:

4 ÷ 16 = 0.25

Step 3: Convert this into a percentage

Now take the output of the last equation, and multiply it by 100 to express it as a percentage:

0.25 x 100 = 25

We can now say the percentage decrease between 16 and 12 is 25%.

Step 4: Confirm it's a percentage decrease

If, after performing the steps above, you’re left with a negative figure, you’re actually dealing with a percentage increase, not a decrease.

In most cases this will be obvious from the start, as with a percentage decrease your original figure will be of greater value than the new figure.

It’s always worth checking though before finalising your answer.

To recap:

Original number - new number = x

x ÷ original number = y

y x 100 = percentage change

A positive result indicates a percentage decrease, a negative result indicates a percentage increase.

Example questions

Below you’ll find three example questions presented as word problems, in the style you’ll meet in a numerical reasoning test. The figures are not necessarily mentioned in the right order, so be sure to read the question carefully before applying the formula.

Example question 1

In 2020, a town had a total population of 17,560. Three years prior, the town’s population was 20,410. What was the percentage decrease of the town’s population over the three-year time frame?

First, determine the order of the values. The original number here is the one given second: 20,410. And 17,560 is our new figure, so:

20,410 - 17,560 = 2,850

2,850 is the decrease of the town’s population. Now divide this by the original population:

2,850 ÷ 20,410 = 0.1396 (to four decimal places)

Multiply this by 100 to determine the percentage decrease:

0.1396 x 100 = 13.96 (to two decimal places)

Answer: The town’s population had decreased by 13.96%

Example question 2

A company’s sales figures indicate that in its first year of trading, it made a gross profit of £28,120. In its second year, gross profit had fallen to £21,950. What was the company’s drop in profit, expressed as a percentage decrease?

This time, our values are given in the correct order, so we subtract the second figure from the first:

28,120 - 21,950 = 6,170

Now take the difference in profit, and divide it by the profit made in year one:

6,170 ÷ 28,120 = 0.2194 (to four decimal places)

Multiply this by 100 to express it as a percentage decrease:

0.2194 x 100 = 21.94 (to two decimal places)

Answer: The company’s gross profit had fallen by 21.94%

Example question 3

A firm’s total liability stood at £1.24 million at the end of year one, and £0.93 million at the end of year two. What is the percentage decrease in total liability?

The original figure is £1.24 million, so first find the decrease:

1.24 - 0.93 = 0.31

Divide the decrease by the original total liability:

0.31 ÷ 1.24 = 0.25

Multiply by 100 to express it as a percentage: