Modulo Operator (%) in C/C++ (original) (raw)

Last Updated : 27 May, 2026

The modulo operator (%) is an arithmetic operator used in C and C++ to find the remainder after dividing one integer by another. It returns the leftover value of an integer division operation.

Used to calculate the remainder of division operations between integers.
Commonly used in loops, checking even/odd numbers, circular indexing, and hashing. C++ `

#include using namespace std;

int main() {

int a = 10, b = 3;

int result = a % b;

cout << "10 % 3 = " << result << endl;

return 0;

}

Syntax

If x and y are integers, then the expression:

x % y;

pronounced as "x mod y".For example, 10 % 2 will be pronounced as " Ten mod Two".

Example

If 10 % 3 is calculated, the result is 1 because dividing 10 by 3 leaves a remainder of 1. Similarly, 8 % 2 returns 0, which indicates that 8 is an even number.

Return Value of Modulo Operator

If y completely divides x, the result of the expression is 0.
If x is not completely divisible by y, then the result will be the remainder in the range [0, y-1]
(x % y) < (x / 2) .........if (x >= y)
(x % y) = x ......... if (x < y)
If y is 0, then division by zero is a compile-time error.

To understand operators and their applications in algorithms, check out our Complete C++ Course, where you’ll learn how to use various operators and functions effectively in C++.

C++ `

#include

using namespace std;

// Driver code int main(void) { int x, y;

int result;

x = 3;
y = 4;

// using modulo operator
result = x % y;
cout << result << endl;

result = y % x;
cout << result << endl;

// for different values
x = 4;
y = 2;

result = x % y;
cout << result;

return 0;

}

C

#include <stdio.h>

int main(void) { int x, y;

int result;

x = 3;
y = 4;
// using modulo operator
result = x % y;
printf("%d", result);

result = y % x;
printf("\n%d", result);

// for different values
x = 4;
y = 2;
result = x % y;
printf("\n%d", result);

return 0;

}

Restrictions

The modulo operator has few restrictions or limitations on it. The % modulus operator cannot be applied to floating-point numbers i.e. float or double. If you try to use the modulo operator with floating-point constants or variables, the compiler will produce an error.

C++ `

#include using namespace std;

// Driver code int main() { float x, y;

x = 2.3;
y = 1.5;

// modulo for floating point values
result = x % y;
cout << result;

return 0;

}

C

#include <stdio.h>

int main(void) { float x, y;

float result;

x = 2.3;
y = 1.5;

// modulo for floating point values
result = x % y;
printf("%f", result);

return 0;

}

**Output

Compilation Error in C code :- prog.c: In function 'main': prog.c:19:16: error: invalid operands to binary % (have 'float' and 'float') result = x % y; ^

Modulo Operator for Negative Operands

The sign of the result for the modulo operator is machine-dependent for negative operands, as the action takes as a result of underflow or overflow.

C++ `

#include using namespace std;

// Driver code int main(void) { int x, y;

int result;

x = -3;
y = 4;

// modulo for negative operands
result = x % y;
cout << result << endl;

x = 4;
y = -2;
result = x % y;
cout << result << endl;

x = -3;
y = -4;
result = x % y;
cout << result;

return 0;

}

C

#include <stdio.h>

int main(void) { int x, y;

int result;

x = -3;
y = 4;

// modulo for negative operands
result = x % y;
printf("%d", result);

x = 4;
y = -2;
result = x % y;
printf("\n%d", result);

x = -3;
y = -4;
result = x % y;
printf("\n%d", result);

return 0;

}

**Note: In C and C++, the sign of the result follows the sign of the dividend (left operand).

**Example

-10 % 3 = -1
10 % -3 = 1

Applications

The modulo operator is widely used in programming for mathematical calculations, looping operations, and data processing tasks.

Used to check whether a number is even or odd.
Used in cyclic operations like circular queues and clock calculations.
Used in hashing algorithms and array indexing.
Used in competitive programming for handling large number operations.