**Take 30% out of a quantity** is quite useful, especially to know the discount and offers that have that particular rebate.

Our percentage calculator will allow you to find out** 30 percent of the number** you need instantly. Just type in the figure, hit the Calculate button and you'll automatically know how much your 30% is. If you need to find out any other percentage, we also have a percent calculator in which you will be able to set the exact amount and percentage.

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## How to calculate 30 percent of an amount

To calculate 30 percent of a number manually **we only have to apply a simple rule of three** like the one below:

In this case, we are left with two unknowns whose value we do not yet know:

- B: Number from which we want to find your 30%
- We would still need to know how much 'Y' is worth, whose value would be 30 percent of the initial number.

We can clear the value we are interested in as follows:

Y = quantity x 30 / 100 = quantity x 0.3

To make it clearer, here is a practical example of how to apply what we have just learned.

## Calculate 30 percent of 50

To obtain the 30% of the number 100, we will use the mathematical expression that we have mentioned above:

Y = = = quantity x 0.3 = 100 x 0.3 = 30

As you can see, it is very easy **calculate 30 percent of any number** multiplying by 0.3.

## Calculate 30 percent in Excel

If you need **calculating 30% using a spreadsheet program **as Excel, the formula to be used is as follows:

=cell*30%

Where we have put 'cell' you have to write the coordinates of the cell where the number you want to calculate the percentage is located. In this way, you will be able to use this application included in Microsoft Office for **calculate percentages automatically** and without wasting time.