• Christian Paul

How To Calculate Percentages

Updated: May 22

One of the most valuable skills in Maths EVER, am I right?

It’s totally underrated – it’s taught at a Year 9 level, and forgotten by the time the students reach Year 12. Then, once they move into the workforce, they have to try and relearn the whole process, despite the fact that it’s so easy!

So, here are some easy steps to make sure you never struggle again.

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Calculating percent of a number.

Take the percentage you wish to find. Let’s use 20% as an example. There is a hidden decimal point at the end of that number (20.0%). Move that decimal two places to the left (Now you should have 0.20). Multiply that decimal by the number you are working with.

Example: To find 35% of 150, move the decimal place two places left to give 0.35, then multiply this by 150. (0.35 x 150 =  52.5)

Calculating “what percentage is that”

If you have 120 out of 700, what percentage do you have?

To calculate, simply divide the smaller number by the bigger number, which will give you a decimal value. Moving the decimal point two spaces right will turn it into a percentage.

Example: 120 out of 700 as a percentage. 120 / 700 = 0.17, then move the decimal two spaces right to give 17%

Adding percent to a number

Increasing a number by a percentage is common in retail or sales.

To increase a number by x%, first consider that the number unchanged would represent 100%. Which means an increase of 20% would bring the total to 120%

Follow the same process as “finding a percentage of a number” using this value. Move the decimal two places to the left, then multiply.

Example: Calculate the price of a $70 item after a 25% increase. This would mean that the new value is 125% of the original. Moving the decimal two places left gives 1.25. Then, 1.25 x $70 = $87.50

Discounting x percent from a number

The reverse of adding an amount. This is easiest if we think that “10% off” actually means “90% remaining”.

With this concept, you can once again follow the same process as above.

Example: Find the price of a $90 item after a 15% discount. 15% off means 85% remaining. Converting to a decimal give 0.85, then multiplying gives 0.85 x $90 = $76.50

Need a bit more help?

Download my free, easy spreadsheet to do the calculations for you! You can download it here

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