Square Root of 81 Here we will define, analyze, simplify, and calculate the square root of 81. We start off with the definition and then answer some common questions about the square root of 81. Then, we will show you different ways of calculating the square root of 81 with and without a computer or calculator. We have a lot of information to share, so let's get started!

Square root of 81 definition
The square root of 81 in mathematical form is written with the radical sign like this √81. We call this the square root of 81 in radical form. The square root of 81 is a quantity (q) that when multiplied by itself will equal 81.

81 = q × q = q2

Is 81 a perfect square?
81 is a perfect square if the square root of 81 equals a whole number. As we have calculated further down on this page, the square root of 81 is a whole number.

81 is a perfect square.

Is the square root of 81 rational or irrational?
The square root of 81 is a rational number if 81 is a perfect square. It is an irrational number if it is not a perfect square. Since 81 is a perfect square, it is rational number. This means that the answer to "the square root of 81?" will have no decimals.

81 is a rational number

Can the square root of 81 be simplified?
A square root of a perfect square can be simplified because the square root of a perfect square will equal a whole number:

81 = 9

How to calculate the square root of 81 with a calculator
The easiest and most boring way to calculate the square root of 81 is to use your calculator! Simply type in 81 followed by √x to get the answer. We did that with our calculator and got the following answer:

81 = 9

How to calculate the square root of 81 with a computer
If you are using a computer that has Excel or Numbers, then you can enter SQRT(81) in a cell to get the square root of 81. Below is the result we got:

SQRT(81) = 9

What is the square root of 81 written with an exponent?
All square roots can be converted to a number (base) with a fractional exponent. The square root of 81 is no exception. Here is the rule and the answer to "the square root of 81 converted to a base with an exponent?":

b = b½

81 = 81½

How to find the square root of 81 by long division method
Here we will show you how to calculate the square root of 81 using the long division method. This is the lost art of how they calculated the square root of 81 by hand before modern technology was invented.

Step 1)
Set up 81 in pairs of two digits from right to left:

 81

Step 2)
Starting with the first set: the largest perfect square less than or equal to 81 is 81, and the square root of 81 is 9. Therefore, put 9 on top and 81 at the bottom like this:

 9 81 81

The difference between the bottom two numbers is zero, therefore, you are done! The answer is the green number on top. Once again, the square root of 81 is 9.

Square Root of a Number
Please enter another number in the box below to get the square root of the number and other detailed information like you got for 81 on this page.

Notes
Remember that negative times negative equals positive. Thus, the square root of 81 does not only have the positive answer that we have explained above, but also the negative counterpart.

We often refer to perfect square roots on this page. You may want to use the list of perfect squares for reference.

Square Root of 82
Here is the next number on our list that we have equally detailed square root information about.