How to find the length of a string in Golang

Key takeaways:

  • String length is essential for various applications, including UI design, text validation, and networking.

  • Methods: len() and RuneCountInString()

    • len(): This returns the number of bytes in a string.

    • RuneCountInString(): This returns the number of characters in a string.

Understanding how to find the length of a string is a fundamental operation. It is difficult to think of a domain that doesn’t require string length at some point—whether in web development, data science, or user interface development, to name a few. Many applications rely on string length:

  • User interface design: Ensure text fits within UI elements to avoid overflow.
  • Text validation: Validate user input against length constraints (e.g., password limits).
  • Networking: Frame network messages correctly by measuring byte length.

Finding the length of a Go string

Go by Griesemer et al. makes finding the length of a string process straightforward. In Golang, we use the following two methods to find Golang string length:

  • len()
  • RuneCountInString()

Method 1: Use the len() method to find the length of a string

The len()function in Golang returns the number of bytes in a string.

Syntax

len(str)

Parameters

This method takes a string str as a parameter.

Return value

This method returns the length of the string.

Code example: Counting the byte length of a string in Golang

The following code demonstrates how to determine Golang string length.

package main
import(
    "fmt"
)
//Program starts from here
func main() {
    //provide the string here
    var str = "educative"
    //calculate length
    var length = len(str)
    //display length
    fmt.Println("Length of the string is :", length)
}

Code explanation

  • Line 8: We call the main() function.
  • Line 10: We declare the string str.
  • Line 13: We pass the string str as a parameter to the len() method. Next, we assign length to the length variable, which is returned by len().
  • Line 16: We use the println() function to print the length.

Method 2: Use the RuneCountInString() method to find the length of a string

The RuneCountInString() method is provided by the utf8 package.

Syntax

RuneCountInString(str)

Parameters

This function accepts a string as its parameter.

Return value

It returns the actual number of characters in the string.

Code example: Counting characters in a string in Golang

The following code demonstrates how to determine Golang string length.

package main
//import utf8 package
import (
    "unicode/utf8"
    "fmt"
)
//Program exection starts here
func main() {
    //provide the string here
    var str = "educative"
    //calculate length
    var length = utf8.RuneCountInString(str)
    //display length
    fmt.Println("Length of the string is :", length)
}

Code explanation

Most of the explanation is the same as for the len() method.

  • Line 5: We import the utf8 package.
  • Line 15: We pass the string str as a parameter to RuneCountInString(). We assign the output length to the length variable.

How to decide which method to use

We have learned two ways to find the length of a string in Golang.

For normal characters, we can use either the len() function or the RuneCountInString() method. However, if the string contains special characters, such as the Black Chess Queen ♛, the len() function will return a length value that represents the number of bytes, not the number of characters. This can be misleading because each special character may occupy multiple bytes. In such cases, it is better to use RuneCountInString(), which accurately counts the number of characters, regardless of how many bytes they occupy.

package main
//import utf8 package
import (
    "unicode/utf8"
    "fmt"
)
//Program exection starts here
func main() {
    //provide the string here
    var str = "Black Chess Queen ♛"
    //calculate length
    var length = utf8.RuneCountInString(str)
    //display length
    fmt.Println("Length of the string by RuneCountInString() is :", length)
    
    //display length
    fmt.Println("Length of the string by len() is :", len(str))
    
}

Want to learn Go and unlock its full potential? The Way to Go course is your perfect starting point! This course will teach you Go's core constructs and advanced concepts like error-handling, networking, and templating and help you master efficient programming techniques. With hands-on projects and real-world examples, you’ll gain the skills to build robust, concurrent applications.

Start your journey to mastering Go today!

Frequently asked questions

Haven’t found what you were looking for? Contact Us

Does len() start from 0?

No, len() starts counting from 1.

Does len() include spaces?

Yes, len() includes all characters in the string, including spaces.

How do we find the length of a string in Java?

To calculate the length of a string in Java, we can use an inbuilt length() method of the Java string class.

Can len() be used for strings with multi-byte characters?

No, len() returns the number of bytes, which may not equal the number of characters for multi-byte characters.

How do we handle strings length with emojis in Golang?

We can use the RuneCountInString() function to count the number of characters instead of the number of bytes to accommodate multi-byte characters like emojis.

Free Resources

Copyright ©2025 Educative, Inc. All rights reserved