Hi, this is Gary with MacMost.com. Today let me show you how to use percentages in Numbers.
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Now I'm often asked about using percentages in Numbers. So let's start with the basic
math behind percentages. A percent is a fractional value based on 100. So let's say you had 400
people and 300 out of those 400 people prefer apples while 100 out of those 400 people prefer
oranges. You would say then 75% of those people preferred apples and 25% preferred oranges.
Where do those numbers come from? Well, if you take 300 and divide by 400 and represented
as a decimal value you get 0.75. 300 divided by 400 equals 0.75. To get the percentage
you simply move the decimal place over two and add a percent symbol or the word percent
afterwards. So 75%. As far as the math is concerned it's still a value of 0.75. But
the way we say it is 75%. They are the same thing just two different ways of saying it.
So if you want to represent say 9 out of 18 people that's 50%. If you want to represent
250 out of 250 people that's 100%. So it's important to realize that 100% is the same
as saying 1.0. It's one whole thing. So when you say 50% it's not really the number 50.
It's 0.5 that you're using.
So let's look at a simple spreadsheet that shows student grades on a test. Let's say
the test had a total of 48 questions on it and let's say the student got 42 of those
questions correct. Now you want to compute a grade that's a percent. Instead of saying
42 out of 48 you want to give a percentage. So the way to do that is simple divide. You
start a formula. I'm going to hit the equals key to do that. You take the number correct
divided by the total and the result will be 0.875. Now we can tell that it's 87.5%. But
we want to actually show that here in the table. So how do we do that? You would do
that simply using Formatting. So I'm going to select the cell here and I'm going to go
to Format, Cell on the right sidebar. I'm going to change the Data Format from Automatic
to Percentage. You could see here it automatically changes it to 87.5%. I've some options here
like the number of decimals. Here it's set to Automatic. But I can change it to say two
decimals and it's always going to show two decimal places. Or I can say zero and it will
always just round to the nearest whole number for the percent.
Now you can also type a percentage. So normally if I wanted to type a percentage, like 75%,
you might think that I could type 75. But that will actually get me 75, a full value
of 75. Which is 75 times 100 and would be the equivalent of 7500%. What you want to
do if you want to type a decimal is do 0.75. That's equivalent to 75%. Now if I would go
to Data Format and change that to Percentage you could see it is indeed 75%. But there's
a shortcut to doing this. You can type 75 and then you put the percent symbol after
it. Numbers will convert that to a percentage. In other words it will move the decimal place
over to the left two and give you value of 0.75. In addition to that it will automatically
format the cell as percentage. So you see 75%. If I select the cell you can see the
actual value of the cell, down here on the bottom left, as 0.75. That is, of course,
very important especially if you're multiplying by that value. There's a big difference between
multiplying by 0.75 or 75%, or multiplying by 75.
Now another common way to use percent in a spreadsheet would be to see how big of a percentage
a single value makes up of a total. So here we have a list of values. It would be nice
to be able to show, next to each value, how much of a percent of the total it is. So in
other words 5, how much does that represent out of the total of all of these. So it's
just simple division and then setting the formatting correctly. So I could take this
value here and then divide it by the total number of values. The way to do that is by
using the Sum function, selecting the column there. So the Sum of all the values. Now I
get that there. If I select it and then change the Data Format to Percentage I get the percentage.
Let's change it from Automatic to Zero. So there is zero decimal places there and that's
approximately 6% of the total. If I were to Copy that and then Paste it in the rest you
could see that it's going to take the percentage of each one. So this is 4%, 8%, and you could
see here this large value represents 41% of the total. The great thing about this is it
will automatically expand. So if I add another row there you could see it's zero percent
because there's no value there. But if I add a number you could see all the percentages
change because now the total has increased by 20 and that decreases the percentage of
each one of these out of the total. So it automatically recalculates. Instead of a big
value here and you could see that large value represents 49% and the other 51% is split
between the rest of these values. It's automatically updated.
Another common use for percentages is when you're calculating Sales Tax on an item. You
would commonly hear, for instance, that there's 7.2% sales tax on an item. Remember that's
not 7.2, that's moving the decimal place over two. So .072. So if you wanted to calculate
sales tax, like here's a sale for $50, you would multiply this not by 7.2 which would
give you 7.2 times the value. You want to move the decimal place over by two. So .072.
So the sales tax on this would be $3.60. But you could also use the percent symbol in formulas.
So we can multiply this by 7.2%. That will automatically convert that to that .072. So
you can see I get this same value there. If we look at the formula down here we could
see it maintains 7.2% as the formatting for that so we can easily read it. We go into
it and we can see it still says 7.2% but that's the equivalent to .072. So if you wanted the
total price you could then go and add these two values together like that. But another
way to do it is to calculate the total price without having the sales tax there. So let's
delete this column here and calculate the total price but using the sale price and then
we could either add the sale price again times 7.2% to get the right value or, the way a
lot of people like to do it, is multiply the sale price by the percent sales tax plus one.
So instead of .072 you would do 1.072. You can see that gives you the correct value.
You could even do it as a percent and say taking 100%, adding 7.2%, and then you get
the correct answer there as well. Or you could just skip the addition there and do 107.2%,
the sum of 100 plus 7.2 represented as percentage. That gives you the correct value as well.
So those are the basics there. To summarize percentages are just a fraction of an individual
item over a total and then you move the decimal place over two and say the word percent afterwards.
So always remember the actual value is something like 0.75 when you say 75%. Don't try to use
whole number values like 75 to represent percent. Use 0.75 and format the cell as
a Percentage.