# Determine the Size and Length of an Array in C

> Use the C sizeof operator to determine the total byte size and element count of an array by dividing the array size by the size of its first element

**URL:** https://sentry.io/answers/determine-the-size-of-an-array-in-c/

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## The Problem

How can I determine the size of and number of elements in an array in C?

## The Solution

We can use the C [`sizeof`](https://en.wikipedia.org/wiki/Sizeof) operator to discover the size of expressions and data types in bytes. Using `sizeof` on an array will return the array's size in bytes, as below:

```c
size_t array_size = sizeof(my_array);
```

The [`size_t`](https://www.gnu.org/software/libc/manual/html_node/Important-Data-Types.html#index-size_005ft) type is used for sizes returned by `sizeof`.

To get the number of elements in our array, we need to divide this value by the size of a single element. Being of the same type, all elements in a C array will also be of the same length, so we can use the first element (`my_array[0]`) to do this:

```c
size_t list_length = sizeof(my_array) / sizeof(my_array[0]);
```

In the background, `size_t` is an unsigned integer or unsigned long. Therefore, unless the size of our array is greater than `INT_MAX`, we can safely declare `list_length` as an `int`:

```c
int list_length = sizeof(my_array) / sizeof(my_array[0]);
```

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*Source: [sentry.io/answers/determine-the-size-of-an-array-in-c/](https://sentry.io/answers/determine-the-size-of-an-array-in-c/)*