---
title: 3.23 sizeof Operator
description: "The `sizeof` operator determines the size, in bytes, of a type or object. Its result has type `size_t`. ``` #include int main() { int number = 10; char letter = 'A'; double value = 3.14; printf(\"Size of int = %zu…"
url: "https://edcret.in/docs/c-programming/operators-and-expressions/3-23-sizeof-operator/"
updated: "2026-09-07"
category: C Programming / Operators and Expressions
---

# 3.23 sizeof Operator

The `sizeof` operator determines the size, in bytes, of a type or object. Its result has type `size_t`.

```
#include <stdio.h>

int main()
{
    int number = 10;
    char letter = 'A';
    double value = 3.14;

    printf("Size of int    = %zu bytes\n", sizeof(int));
    printf("Size of number = %zu bytes\n", sizeof(number));
    printf("Size of char   = %zu bytes\n", sizeof(letter));
    printf("Size of double = %zu bytes\n", sizeof(value));

    return 0;
}
```

### Example Output

The exact sizes are implementation-dependent. A common result is:

```
Size of int    = 4 bytes
Size of number = 4 bytes
Size of char   = 1 bytes
Size of double = 8 bytes
```

### Explanation

`sizeof` can be applied to a type:

```
sizeof(int)
```

or to an expression/object:

```
sizeof(number)
```

When applied to an object, it gives the number of bytes required to store that object's type.

The result is of type `size_t`, so `%zu` is used with `printf()`:

```
printf("%zu\n", sizeof(number));
```

The size of `char` is always `1` byte in C, while the number of bytes occupied by other types depends on the implementation.

`sizeof` does not evaluate its operand when the operand is an expression whose type is not a variable length array. For example:

```
sizeof(number++)
```

does not perform the increment.