Content

• To step
• Method 1 of 3: Calculate the percentage of a whole
• Method 2 of 3: Calculate the other way around with a percentage as the starting point
• Method 3 of 3: Calculate discounts
• Tips

Percentages can be found all around us - from 3.4% interest to 80% off. It is therefore useful to know what percentages are, what they mean and how to calculate them. It's not as difficult as you may think. Below you can read how you can calculate percentages in different ways.

To step

Method 1 of 3: Calculate the percentage of a whole

1. Know what a percentage is. A percentage is a way of indicating with a number how large the share in the total is. To calculate a percentage, consider the total as 100%. For example, you can say that you have 10 apples (= 100%). If you eat two apples, you have eaten 2/10 × 100% = 20% of the apples and you have 80% of the original amount of apples left.
   • The word "percentage" comes from the Italian per cento or the French pour cent and literally means per hundred.
2. Determine how much the total is. For example, let's say we have a pot of 1199 red marbles and 485 blue marbles. If we add those up, we get 1684 marbles. In this case, 1684 is the total number of marbles in the pot and therefore equal to 100%.
3. Find the number you want to convert to a percentage. Let's say we want to calculate how many percent the number of blue marbles is out of the total number of marbles in the pot.
4. Put these two numbers into a fraction. In our example, we want to know what percentage is 485 (the number of blue marbles) of 1684 (the total number of marbles). Therefore, the fraction becomes 485/1684 in this case.
5. Convert the fraction to a decimal number. To convert 485/1684 to a decimal, divide 485 by 1684. The result is 0.288.
6. Convert the decimal number to a percentage. Multiply the result from the previous step by 100. So, in our example, we multiply 0.288 by 100, which gives the result 28.8 or 28.8%.
   • An easy way to multiply a decimal number by 100 is to place the decimal point two places to right to slide.

Method 2 of 3: Calculate the other way around with a percentage as the starting point

1. Understand why you should be able to calculate the other way around. Sometimes you only know the percentage of a certain quantity and you have to calculate what its numerical value is. Examples include calculating tax, tips and interest on a loan.
2. Know which numbers to start calculating with. Suppose you borrowed money from a friend who charges interest on it. You originally borrowed € 15 and the interest rate is 3% per day. These are the only two numbers you need for your calculation.
3. Convert the percentage to a decimal number. Multiply the percentage by 0.01 or just shift the decimal two places to left. In our example, that means that 3% becomes 0.03.
4. Multiply the original number by the new decimal number. In this case, you have to multiply 15 by 0.03. The result of this is € 0.45. In this example, that means that you have to pay $ 0.45 in interest for each day that you do not pay back your friend.

Method 3 of 3: Calculate discounts

1. Know the original price and discount percentage. This is a very simple way to calculate a discount price, but you must know exactly what the discount percentage is. So check carefully how much percent discount is given.
2. Determine the opposite number of the discount percentage. You calculate this by reducing 100% with the discount percentage that you are working with. If you want to buy a shirt with a 30% discount, the opposite number is 70%.
3. Convert the opposite percentage to a decimal number. To convert a percentage to a decimal number, multiply it by 0.01 or move the decimal point two places to left. So, in this example, 70% becomes 0.7.
4. Multiply the original price by the new decimal number. If the original price of the shirt you want is $ 20, multiply it by 0.7. The result is 14. This means that the shirt has a discounted price of € 14, -.

Tips

• With a pie chart you can show percentages visually. The whole circle represents 100%. The different parts of the circle represent percentages of the whole, where each part is less than 100% or the whole circle.