How to find the size of data type using sizeof() operator in C

Sizeof(type) is a unary operator used to calculate the size(in bytes) of any datatype in C.

Syntax:

sizeof(type)
Note: type must be replaced by a valid C data type or variable.

Example:

#include <stdio.h>

int main()
{
    int i;
    printf("Size of int = %d\n", sizeof(int));
    printf("Size of i = %d\n", sizeof(i));
    return 0;
}

Output:

Calculating the size of struct and array:

#include <stdio.h>

struct Student {
    int roll; //Will take 4 bytes
    char name[30] //Will take total 1*30 bytes
}stu;

int main()
{
    printf("Size of Student = %d\n", sizeof(struct Student));
    printf("Size of Student = %d\n", sizeof(stu));
    printf("Size of Student.roll = %d\n",sizeof(stu.roll));
    printf("Size of Student.name = %d\n",sizeof(stu.name));

    return 0;
}

Output: Note: size of struct should be 34 bytes buts its takes 36 bytes because the compiler adds extra 1 byte for alignment and performance at the end of each structure members.

Program to calculate size of different data types:

#include <stdio.h>

int main()
{
    printf("Size of char = %d\n", sizeof(char));
    printf("Size of short = %d\n", sizeof(short));
    printf("Size of int = %d\n", sizeof(int));
    printf("Size of long = %d\n", sizeof(long));
    printf("Size of long long = %d\n", sizeof(long long));
    printf("Size of float = %d\n", sizeof(float));
    printf("Size of double = %d\n", sizeof(double));
    printf("Size of long double = %d\n", sizeof(long double));

    return 0;
}

Output:
Note: All size are in bytes and may vary on different platform.