Square Root

Last Updated: June 21, 2024

Square Root

The square root of a number is a critical mathematical concept that acts as the inverse operation of squaring. This operation allows us to find a value that, when multiplied by itself, yields the original number. Represented by the radical symbol ‘√’, the square root can be understood through the equation x=√y or x² = y, where x is the square root of y. While the square of a number (e.g., 3² = 9) gives a positive result, finding the square root (e.g., √9 = 3) often requires specific methods, especially for numbers that are not perfect squares. This concept extends to all numbers, with each having two square roots, a positive and a negative one, although typically only the positive root is denoted as the square root.

What is Square Root?

The square root of a number is a special value that, when multiplied by itself, returns the original number. It’s closely linked to the idea of squaring a number. For example, if we square the number 3 (meaning we multiply 3 by itself), we get 9. This is written as 3 × 3 or 3². Now, if we talk about square roots, it’s like doing the opposite. The square root of 9 is 3, because 3 is the number that produces 9 when multiplied by itself. Mathematically, this is shown as √9 or 9^(1/2), indicating that the square root is the same as raising a number to the power of 1/2.

How to find Square Root?

Finding the square root of a number is to determine which number, when multiplied by itself, equals the original number. There are several methods to find square roots, each suitable for different kinds of numbers.

1. Finding Square Root Using Trial and Error Method

This method involves guessing the square root of a number and refining the guess based on its square.

  • Step 1: Make an initial guess of what the square root might be.
  • Step 2: Square your guess. If the result is too high or too low, adjust your guess accordingly.
  • Step 3: Repeat the process until you find a number whose square exactly equals the original number.

To find √16, you might guess 4. Since 4² = 16, your guess is correct.

2. Square Root by Prime Factorization Method

Prime factorization involves breaking down a number into its prime factors and identifying pairs of identical factors.

  • Step 1: Divide the original number into its prime factors.
  • Step 2: Group the prime factors into pairs of identical numbers.
  • Step 3: For each pair of identical factors, take one number out of the square root.
  • Step 4: Multiply these numbers together to get the square root of the original number.

Formula: √(a² × b² × c² × …) = a × b × c × …

Examples: To find √144, note that 144 = 2² × 2² × 3². So, √144 = 2 × 2 × 3 = 12.

3. Repeated Subtraction Method of Square Root

  • Step 1: Pick the number you want to find the square root of. Make sure it’s a perfect square.
  • Step 2: Subtract odd numbers from your chosen number, starting with 1, then 3, then 5, and so on.
  • Step 3: Count each subtraction you make. This number will be important for finding your answer.
  • Step 4: Keep subtracting until you get down to zero. If the number is a perfect square, you’ll get to zero exactly.
  • Step 5: The total number of subtractions you made is the square root of your original number.

Example: Square Root of 16

  • 16 – 1 = 15
  • 15 – 3 = 12
  • 12 – 5 = 7
  • 7 – 7 = 0
  • Start with 16.
  • Subtract odd numbers in order: 1, then 3, then 5, then 7.
  • It takes 4 subtractions to get to zero.
  • So, the square root of 16 is 4.

This method is easy to understand and shows how square roots work, especially useful for learning with smaller, perfect square numbers.

3. Calculating Square Root by Long Division Method

The long division method is a systematic approach suitable for finding the square roots of both perfect and non-perfect squares.

  • Step 1: Place a bar over every pair of digits starting from the decimal point (or the unit’s place if there’s no decimal).
  • Step 2: Find the largest number whose square is less than or equal to the first set of numbers under the leftmost bar. Place this number above the bar.
  • Step 3: Subtract the square of the number you found from the number under the bar and bring down the next set of digits next to the remainder.
  • Step 4: Double the number above the bar (the divisor) and find a new digit that, when added to the divisor and multiplied by the same digit, is less than or equal to the remainder. Add this digit to the top.
  • Step 5: Repeat Steps 3 and 4 until all digits have been brought down.

Example: Finding √1225 involves dividing it into pairs (12 and 25), guessing the first digit of the root, subtracting its square, and continuing the process with what remains.

4. Finding Square Root Using a Calculator

For most practical purposes, calculators provide the quickest and most accurate square roots.

  • Step 1: Enter the number whose square root you want to find into the calculator.
  • Step 2: Press the square root button (√) to get the result instantly.

Example: Inputting 144 and pressing √ yields 12.

5. Finding Square Root by Estimation Method

Estimation is useful when an approximate square root is sufficient, especially if the number is not a perfect square.

  • Step 1: Find the nearest perfect squares above and below the given number.
  • Step 2: Estimate that the square root of your number lies between the square roots of these perfect squares.
  • Step 3: Refine your estimate based on how close the number is to the lower or upper bounds.

Example: For √50, since 49 (7²) is below and 64 (8²) is above, estimate √50 to be between 7 and 8, closer to 7.

6. Calculation of Square Root by Graphical Method

This method uses the curve of the equation y = x² to find square roots graphically.

  • Step 1: Plot the curve y = x² on graph paper.
  • Step 2: Draw a horizontal line at y equals the number whose square root you’re finding.
  • Step 3: The points where the horizontal line intersects the curve give the square roots of the number.

Example: To find √49, draw a horizontal line at y = 49 across the curve y = x². The points of intersection at x = 7 (and x = -7) give the square roots.

Square Root Table

NumberSquare RootNumberSquare RootNumberSquare Root

Square Root of Numbers

Square Root of 1Square Rootof 2Square Rootof 3Square Rootof 4Square Root of 5
Square Rootof 6Square Rootof 7Square Rootof 8Square Rootof 9Square Rootof 10
Square Root of 11Square Root of 12Square Root of 13Square Rootof 14Square Rootof 15
Square Rootof 16Square Rootof 17Square Rootof 18Square Rootof 19Square Rootof 20
Square Root of 21Square Root of 22Square Root of 23Square Rootof 24Square Rootof 25
Square Rootof 26Square Rootof 27Square Rootof 28Square Rootof 29Square Rootof 30
Square Root of 31Square Root of 32Square Root of 33Square Rootof 34Square Rootof 35
Square Rootof 36Square Rootof 37Square Root of 38Square Root of 39Square Rootof 40
Square Rootof 41Square Rootof 42Square Root of 43Square Rootof 44Square Rootof 45
Square Root of 46Square Root of 47Square Rootof 48Square Rootof 49Square Rootof 50
Square Root of 51Square Rootof 52Square Root of 53Square Root of 54Square Root of 55
Square Rootof 56Square Root of 57Square Rootof 58Square Root of 59Square Rootof 60
Square Rootof 61Square Root of 62Square Root of 63Square Rootof 64Square Root of 65
Square Root of 66Square Root of 67Square Root of 68Square Rootof 69Square Rootof 70
Square Root of 71Square Rootof 72Square Root of 73Square Root of 74Square Rootof 75
Square Root of 76Square Root of 77Square Root of 78Square Root of 79Square Rootof 80
Square Rootof 81Square Root of 82Square Root of 83Square Root of 84Square Rootof 85
Square Root of 86Square Root of 87Square Root of 88Square Root of 89Square Rootof 90
Square Root of 91Square Root of 92Square Root of 93Square Root of 94Square Root of 95
Square Rootof 96Square Root of 97Square Rootof 98Square Rootof 99Square Rootof 100

Each entry represents the square root of the corresponding number from 1 to 100. For example, the square root of 1 is 1, the square root of 2 is approximately 1.414, and so on up to the square root of 100, which is 10.

Square Root Formula

The square root formula is used to find the square root of a number, which is the value that, when multiplied by itself, equals the original number. The formula is expressed as:



  • x​ represents the square root of x,
  • y is the value that, when squared (y²), equals x.

For example, if x=9, then 9=3 because 3²=9.

This formula is fundamental in mathematics for solving problems involving square roots, including equations and understanding geometric properties.

Properties of Square Root

  1. Product Rule: The square root of two numbers multiplied together is the same as multiplying the square roots of each number.
    • Example: √(a × b) = √a × √b
  2. Quotient Rule: The square root of a fraction is the same as the square root of the numerator divided by the square root of the denominator.
    • Example: √(a/b) = √a / √b
  3. Square of a Square Root: Taking the square root of a squared number brings you back to the original number’s absolute value.
    • Example: √(a²) = |a|
  4. Non-negative Roots: Square roots are only real and non-negative for non-negative numbers.
    • Example: √a is real only if a ≥ 0
  5. Zero’s Square Root: The square root of zero is zero.
    • Example: √0 = 0
  6. Square Root of One: The square root of one is one.
    • Example: √1 = 1
  7. Adding and Subtracting: You can only directly add or subtract square roots if the numbers inside the square root (radicands) are the same.
    • Example: √a + √a = 2√a
  8. Irrational Numbers: The square root of a non-perfect square is an irrational number, which cannot be exactly represented as a fraction or a terminating or repeating decimal.
    • Example: √2 is irrational.

Square Root of a Negative Number

The concept of the square root of a negative number introduces us to the realm of complex numbers. In traditional real number arithmetic, a square root of a negative number does not exist because no real number squared gives a negative result. However, in the complex number system, there is a special number denoted as “i,” known as the imaginary unit, which is defined by the property that i2=−1.

Understanding the Imaginary Unit “i”

  • The square root of -1 is defined as i.
  • Therefore, the square root of any negative number can be expressed in terms of i. For example, √−4​ can be written as √4×√−1​ or 2i.


Let’s calculate the square root of √-16:

  • First, ignore the negative sign and find the square root of 16, which is 4.
  • Since the number was negative, we then multiply our result by i to get the final answer.
  • Therefore, −16​=4i.

Square Root of Perfect squares

Perfect squares are the squares of whole numbers. The square root of a perfect square is always a whole number.

1² = 1 ⇔ √1 = 1
2² = 4 ⇔ √4 = 2
3² = 9 ⇔ √9 = 3
4² = 16 ⇔ √16 = 4
5² = 25 ⇔ √25 = 5
6² = 36 ⇔ √36 = 6
7² = 49 ⇔ √49 = 7
8² = 64 ⇔ √64 = 8
9² = 81 ⇔ √81 = 9
10² = 100 ⇔ √100 = 10

Square Root of Decimal

The square root of a decimal follows the same basic principle as finding the square root of whole numbers: it’s about finding a number that, when multiplied by itself, results in the original decimal. However, because the original number is a decimal, the square root will often be a decimal as well.

Example: Find the Square Root of 0.09

  1. Start with the Equation: Let’s say we want to find N where N²=0.16.
  2. Take the Square Root of Both Sides: This gives us N=±0.16​.
  3. Understand the Multiplication: We know that 0.4×0.4=(0.4)²=0.16
  4. Simplify: So, N=±(0.4)²​.
  5. Conclude: Therefore, N=±0.4.

Applications of Square Roots

1. Mathematics and Geometry

  • Pythagorean Theorem: One of the most classic applications of square roots is in the Pythagorean theorem. This theorem states that in a right-angled triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides. Calculating the length of any side involves taking the square root of a number.
  • Solving Quadratic Equations: Square roots are essential in solving quadratic equations. When determining the roots of a quadratic equation of the form ax^2 + bx + c = 0, the quadratic formula involves square roots.

2. Physics and Engineering

  • Calculating Velocity and Acceleration: In physics, square roots are used to calculate the velocity of an object when its acceleration and the time taken are known. Similarly, they are used in formulas to find the distance covered under constant acceleration.
  • Resonance Frequencies: In engineering, particularly in electrical engineering, square roots are used to calculate resonance frequencies of circuits, which is crucial for designing filters and oscillators.

3. Computer Graphics

  • Distance Between Points: Square roots are used to calculate the distance between two points in space, whether in 2D or 3D. This is essential in computer graphics for rendering scenes accurately and in developing games to calculate movements or distances between objects.

4. Statistics and Data Analysis

  • Standard Deviation: In statistics, the square root is used in the calculation of the standard deviation, which measures the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean of the set, while a high standard deviation indicates that the values are spread out over a wider range.

5. Finance

  • Compound Interest: In finance, square roots (or roots in general) are used to calculate the time it takes for an investment to grow to a certain amount or to calculate the interest rate required to achieve a certain growth over a specified period.

6. Architecture and Design

  • Golden Ratio: The square root of 5 is a key component in the golden ratio, a proportion often used in art, architecture, and design for its aesthetically pleasing properties. The golden ratio is believed to represent the most aesthetically pleasing proportion between two quantities.

7. Medicine and Health Sciences

  • Drug Dosage Calculations: In health sciences, square roots are sometimes used in calculating the correct dosage of drugs, especially in determining the area of a patch for transdermal medication delivery based on the dosage rate.


What means √?

The √ symbol denotes the square root, which is a value that, when multiplied by itself, returns the original number.

How do you find √?

To find the square root (√) of a number, you can use methods like factorization, estimation, or a calculator for precise or complex numbers.

What is the square √ 64?

The square root of 64 is 8, because 8 multiplied by itself (8 x 8) equals 64.

How do you use √?

Use the square root (√) in mathematics to solve equations, in geometry to find side lengths, and in real-life scenarios like estimating distances or areas.

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