Converting a string to an integer in Go

Clive B.

—December 15, 2024

The ProblemThe Problem

You don’t know how to convert a string to an integer in Go.

The SolutionThe Solution

The simplest way to convert a string to an integer is to use the Atoi function from the strconv package.

For example, you can convert the string "123" to the value 123 as follows:

package main

import (
    "fmt"
    "log"
    "strconv"
)

func main() {
    example := "123"
    integer, err := strconv.Atoi(example)
    if err != nil {
        log.Fatal("failed to convert string to integer", err)
    }

    fmt.Println(integer + 1)
}

This prints the sum of the integer plus one:

124

For performance reasons (and convenience), the above example assumes that your integer is a base-10 signed integer.

If you need more control, you can use the ParseInt function from the same package:

package main

import (
    "fmt"
    "log"
    "strconv"
)

func main() {
    hexadecimal := "7b"
    integer, err := strconv.ParseInt(hexadecimal, 16, 32)
    if err != nil {
        log.Fatal("failed to convert string to integer", err)
    }

    fmt.Println(integer + 1)
}

This prints the sum of the integer plus one:

124

Note: Although the above example uses base 16 and bit size 32, ParseInt still returns a 64-bit integer.

Converting Strings to Other Numerical TypesConverting Strings to Other Numerical Types

If you want to convert a string to another numerical type, you can use the ParseFloat, ParseUint, or ParseComplex functions, also from the strconv package.