Knowing how to calculate the percentage increase is very useful in many situations. While watching the news, you may often hear information on increases presented in (large) numbers without mentioning a percentage to explain the context. After you calculate the percentage increase yourself, which turns out to be only 2%, you can just ignore the horrendous news.
Step
Method 1 of 2: Calculating the Percentage Increase
Step 1. Write down the starting and ending numbers
For example, say your insurance premium has increased. Write down the numbers:
- Before the increase, your car insurance premium IDR 400,000. This is the starting number.
- After the increase, the premium becomes Rp450.000. This is the final number.
Step 2. Calculate the magnitude of the increase
Subtract the starting number from the final number to find out how big the increase is. In this calculation, we are still using numbers, not percentages.
In this example, premium increase = IDR 450,000 – IDR 400,000 = IDR 50,000.
Step 3. Divide the result of subtraction by the initial number
Percentages are a special form of fractions. For example, “5% doctors” is a quick way to write “5 out of 100 doctors”. Once the result of the subtraction is divided by the initial number, we get a fraction that compares the two numbers.
In this example, IDR 50,000/IDR 400,000 = 0, 125.
Step 4. Multiply the result by 100
With this multiplication, the result of the division is converted into a percentage.
The final result of the calculation of the increase in insurance premiums = 0.125 x 100 = 12, 5%.
Method 2 of 2: Using Other Methods
Step 1. Write down the starting and ending numbers
This time we use another example. The world population grew from 5,300,000,000 people in 1990 to 7,400,000,000 people in 2015.
There are tips for solving problems with numbers that have lots of zeros. Instead of counting with a long line of zeros at each step, we can write 5, 3 billion and 7, 4 billion.
Step 2. Divide the final number by the starting number
The results of this calculation show the magnitude of the increase between the final number and the initial number.
- 7, 4 billion: 5, 3 billion = close to 1, 4.
- Round to the significant digits according to the numbers in the problem.
Step 3. Multiply by 100
The result of this multiplication shows the percentage which is a comparison of two numbers. If the number increases (rather than decreases), your answer must always be greater than 100.
1, 4 x 100 = 140%. This means that, in 2015, the world's population was 140% of the population in 1990.
Step 4. Subtract 100
In a problem like this, "100%" is the percentage of the starting score. By subtracting 100% from the answer, we get the percentage increase.
- So, population increase = 140% - 100% = 40%.
- This applies according to the formula for initial value + increment = final value. By rearranging this equation, we get the formula increment = final value - initial value.
Tips
- The magnitude of the increase is commonly referred to as the change in absolute is the number obtained from the result of subtraction. The increase in the price of clothes by Rp. 50,000 and the increase in the price of houses by Rp. 50,000 are the same increase in magnitude absolute.
- You can calculate the percentage drop in the same way. The result you get is a negative number indicating that the number is getting smaller.
- The percentage increase is the change in relatively which shows the magnitude of the increase in the final number to the initial number. The increase in the price of clothes by Rp. 50,000 is a relatively large increase. The increase in house prices of IDR 50,000 is a relatively small increase.
