Python math.sqrt() function | Find Square Root in Python

Last Updated : 14 Feb, 2025

math.sqrt() returns the square root of a number. It is an inbuilt function in the Python programming language, provided by the math module. In this article, we will learn about how to find the square root using this function.

Example:

Python

import math 

# square root of  0 
print(math.sqrt(0)) 

# square root of 4
print(math.sqrt(4)) 

# square root of 3.5
print(math.sqrt(3.5))

Output

0.0
2.0
1.8708286933869707

We need to import math before using this function.

import math

math.sqrt() syntax

math.sqrt(x)

Parameter:

x: A number greater than or equal to 0.

Returns:

The square root of the number x.

math.sqrt() examples

Let's look at some different uses of math.sqrt() .

Example 1: Check if number is prime

math.sqrt() can be used to optimize prime number checking. We only need to check divisibility up to the square root of the number.

Python

import math

n = 23 # Check if 23 is prime

# Check if n is equal to 1
if n == 1:
    print("not prime")
else:
    
    # Loop from 2 to the square root of n 
    for x in range(2, int(math.sqrt(n)) + 1):
        if n % x == 0:
            print("not prime")
            break  # Exit the loop
    else:
        print("prime")

Output

prime

Explanation

If n > 1, we check for factors from 2 to sqrt(n).
If any divisor is found, it prints "Not prime".
If no divisors are found, it prints "Prime".

Example 2: Finding hypotenuse of a triangle

We can use math.sqrt() to find the hypotenuse of a right-angled triangle using the Pythagorean theorem.

Python

a = 10
b = 23
import math

c = math.sqrt(a ** 2 + b ** 2)
print(c)

Output

The value for the hypotenuse would be  25.079872407968907

Explanation

The formula used is c = sqrt(a^2 + b^2).
It calculates the hypotenuse c using the values of a and b.

Error handling

math.sqrt() does not work for negative numbers. It raises a ValueError if we pass a number less than 0.

Python

import math

# error when x<0
print(math.sqrt(-1))

Output

Traceback (most recent call last):
  File "/home/67438f8df14f0e41df1b55c6c21499ef.py", line 8, in 
    print(math.sqrt(-1)) 
ValueError: math domain error

Explanation