{

# Golang Example - Convert Hexadecimal to/from Integer Number In this blog post, You will learn two programs in the Go language. The first program is to convert Hexadecimal to Decimal Integer. The second program is to convert Decimal to Hexadecimal numbers.

Hexadecimal number is also called Hexa number which contains 16 digits i.e numbers start from 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F. It is based on Base 16. i.e Hexa number system. So Hexa Decimal contains Decimal Numbers,0-9 (base 10) and Extra 6 alphabets - A to F

In Golang, Hexadecimal numbers are always either prefixed with 0x or 0X or normal numbers. Example Hexadecimal number is 0x12F or 0X34A,23A.

Decimal Numbers are numbers that contain numbers based on base 10. i.e numbers starting from 0 to 9, Example decimal Number is 25

The below programs takes input from a user keyboard console and store it in the corresponding variable.

## How to convert from Hexadecimal to Decimal Number in Golang?

We have 2 ways to cast Hexadecimal to decimal numbers as follows.

• using strconv ParseInt function
• Using strconv ParseUint function

### strconv ParseInt function example to cast Hexa to Decimal Integer

`strconv` package provides the `ParseInt` function, which does the conversion of different types.

A parseInt function use to convert a given string in Hexa format, convert to a Decimal number.

Please note that the base supplied to this function is 16.

Given the input, the string stores the variable hexaNumber.

valid hexaNumber values accepts values - 23a,0x23a,0X23a.

if hexaNumber string prefixed with 0x, or 0X, strconv.ParseInt() throws error strconv.ParseInt: parsing “0x23A”: invalid syntax

So we have to write a function to replace 0x or 0X with an empty string.

Here is a complete function to replace long hexadecimal numbers

``````func hexaNumberToInteger(hexaString string) string {
// replace 0x or 0X with empty String
numberStr := strings.Replace(hexaString, "0x", "", -1)
numberStr = strings.Replace(numberStr, "0X", "", -1)
return numberStr
}
``````

Here is a complete example for Casting a long Hexadecimal number to a decimal Integer

``````package main

import (
"fmt"
"math"
"strconv"
"strings"
)
func hexaNumberToInteger(hexaString string) string {
// replace 0x or 0X with empty String
numberStr := strings.Replace(hexaString, "0x", "", -1)
numberStr = strings.Replace(numberStr, "0X", "", -1)
return numberStr
}

func main() {
var hexaNumber string
fmt.Scanln(&hexaNumber)
output, err := strconv.ParseInt(hexaNumberToInteger(hexaNumber), 16, 64)
if err != nil {
fmt.Println(err)
return
}
fmt.Printf("Output %d", output)
}

``````

When the above program is compiled and executed, the Output is

``````Enter Hexadecimal Number:23a
Output 570
``````

For Example, If the input number gave as 23a, Output is 570 Output is returned with calculated 2*16*16+3*16+10*16

### strconv ParseUint function example to convert Hexadecimal to number

`strconv` package provides various functions for `signed` and `unsigned` numbers.

Like `ParseInt` function, `ParseUint` function is used to convert unsigned integer. The `ParseInt` function is used to convert a given string in Hexa format, convert to a Decimal number.

Please note that the base supplied to this function is 16.
Here is an example program that converts Hexadecimal to a decimal number of type uint64

``````package main

import (
"fmt"
"strconv"
"strings"
)

func hexaNumberToInteger(hexaString string) string {
// replace 0x or 0X with empty String
numberStr := strings.Replace(hexaString, "0x", "", -1)
numberStr = strings.Replace(numberStr, "0X", "", -1)
return numberStr
}

func main() {
var hexaNumber string
fmt.Scanln(&hexaNumber)
output, err := strconv.ParseUint(hexaNumberToInteger(hexaNumber), 16, 64)
if err != nil {
fmt.Println(err)
return
}
fmt.Printf("Output %d", output)
}

``````

The output of the above program is

``````Enter Hexadecimal Number:0x25
Output 37
``````

### Example Program to convert Decimal to HexaDecimal Number

We have 2 ways to convert Decimal to HexaDecimal numbers in Golang. Below are two ways as follows

• using strconv FormatInt function
• using strconv FormatUint function

The below program takes decimal input numbers from the keyboard console and stores them in variable decimal.

### strconv FormatInt function example to convert Decimal to Hexa Number

Inbuilt Standard package `strconv` provides the `FormatInt` function used to convert Decimal to Hexa number.

Here is an example program for Casting Decimal integer to Hexa number

``````package main

import (
"fmt"
"strconv"
)

func main() {
var decimal int64
fmt.Print("Enter Decimal Number:")
fmt.Scanln(&decimal)
output := strconv.FormatInt(decimal, 16)
fmt.Print("Output ", output)

}

``````

Output is

``````Enter Decimal Number:29
Output 1d
``````

### strconv FormatUint function example to convert Decimal to Hexadecimal Number

strconv package FormatUint function which converts of `Uint64` to `hexadecimal` number.

Here is an example program for Casting an unsigned integer to a Hexadecimal number.

``````package main

import (
"fmt"
"strconv"
)

func main() {
var decimal uint64
fmt.Print("Enter Decimal Number:")
fmt.Scanln(&decimal)
output := strconv.FormatUint(decimal, 16)
fmt.Print("Output ", output)

}

``````

Output:

``````Enter Decimal Number:30
Output 1e
``````

## Conclusion

You learned to Convert Hexadecimal to number and number to hex using inbuilt functions and writing custom functions.

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