# Calculating With Percentages

Calculating with percentages is easy and it is all in the wording, the manner of expressing of how it is done in words that either makes it easy or difficult to understand. And to say the least, that can make calculating with percentages confusing.

For me the easiest way of calculating a percentage of an amount is to divide the amount by 100 to get the 1% value and then multiply that with the percentage amount.

### Calculating a percentage of an amount

Starting amount = 240, take this amount as being 100%
Percentage = 12%

if 100% = 240 then 1% = 240 / 100 = 2.40
if 1% = 2.40 then 12% = 12 * 2.40 = 28.8
12% of 240 = 28.8

Using fraction format
Make it even more confusing
Starting amount = 240 =100%
Percentage = 12%

As a fraction this becomes 12/100 * 240 = divide numerator by the denominator 12/100 = 0.12 and multiply this by the starting amount 0.12 * 240 = 28.8

Using decimal format
A much simpler way
Starting amount = 240 =100%
Percentage = 12%

Convert the 12% to a decimal number by dividing it by the starting amount which = 100%
then 12 / 100 = 0.12
0.12 * 240 = 28.8

All three ways of calculating are correct and produce a similar result!

### Calculating a Discount Percentage

If a discount in percentage is offered that means that the starting amount is reduced by the percentage discount. If the starting amount = 100% and discount = 24% then the final amount = 76% of the starting amount.

Example
Starting amount = \$ 369.55 discount = 11%
If 100% = 369.55 then 1% = 369.55/100 = 3.6955
if 1% = 3.6955 then 11% = 11 * 3.6955 = 40.6505
then 369.55 - 11% = 369.55 - 40.6505 = 328.8995 rounded to two digits = 328.90
Starting price of \$ 369.55 with an 11% discount becomes a final price of \$328.90

Using decimal format
Starting amount = \$ 369.55 discount = 11%
\$ 369.55 = 100% then an 11% discount = a final price which = 89% of the starting amount.
Change 89% to a decimal by dividing by 100 -------- 89 / 100 = 0.89
Multiply the starting amount by this number:
\$ 369.55 * 0.89 = 328.8995 rounded to two digits = \$328.90

### Calculating a Surcharge Percentage

If a surcharge in percentage is added to an amount, that means that the starting amount is increased by the percentage amount. If the starting amount = 100% and surcharge = 30% then the final amount will equal 130% of the starting amount.

Starting amount = 1000 Surcharge percentage = 30%
If 100% = 1000 then 1% = 1000/100 = 10
if 1% = 10 then 30% = 30 * 10 = 300
then 1000 + 30% = 1000 + 300 = 1300

Using decimal format
Starting amount = 1000 Surcharge percentage = 30%
if 1000 = 100% and the surcharge is 30% the final price will be 130% 0f 1000
change 130 into a decimal by dividing by 100-130/100 = 1.30
Multiply the starting amount by this number:
1000 * 1.30 = 1300