Home C++ Programming Tutorials Ceil and Floor functions in C++

# Ceil and Floor functions in C++

The floor and ceiling functions map a real number to the greatest preceding or the least succeeding integer, respectively.

floor(x) : Returns the largest integer that is smaller than or equal to x (i.e : rounds downs the nearest integer).

```// Here x is the floating point value.
// Returns the largest integer smaller
// than or equal to x
double floor(double x)  ```

Examples of Floor:

```Input : 3.5
Output : 3

Input : -3.1
Output : -4

Input : 1.9
Output : 1```
``````// C++ program to demonstrate floor function
#include <iostream>
#include <cmath>
using namespace std;

// Driver function
int main()
{
// using floor function which return
// floor of input value
cout << "Floor is : " << floor(3.3) << endl;
cout << "Floor is : " << floor(-3.3) << endl;

return 0;
}
``````

Output:

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```Floor is : 3
Floor is : -4```

ceil(x) : Returns the smallest integer that is greater than or equal to x (i.e : rounds up the nearest integer).

```// Here x is the floating point value.
// Returns the smallest integer greater
// than or equal to x
double ceiling(double x)  ```

Examples of Ceil:

```Input : 29.5
Output : 30

Input : -23.1
Output : -24

Input : 21.9
Output : 22```
``````// C++ program to demonstrate ceil function
#include <iostream>
#include <cmath>
using namespace std;

int main()
{
// using ceil function which return
// floor of input value
cout << " Ceil is : " << ceil(3.3) << endl;
cout << " Ceil is : " << ceil(-6.3) << endl;

return 0;
}
``````

Output:

```Ceil is : 4
Ceil is : -7```