C Math

Definition and Usage

C has no built-in x^2 operator or Math class like some languages. For roots, powers, trigonometry, logs, and rounding you call library functions from <math.h>—for example sqrt(x), pow(x, y), and sin(angle).

Operators vs math.h

Everyday arithmetic uses operators: +, -, *, /, %. When you need square roots, angles, or careful decimal rounding, switch to math.h. Integer absolute value abs() lives in <stdlib.h> instead.

What should beginners learn first?

Include <math.h>, compile with -lm on GCC/Clang, then practice fabs(), sqrt(), pow(), and sin() with radian conversion. Those cover absolute value, roots, powers, and basic trigonometry.

This lesson vs the Functions index

This page is the C math lesson: setup, radians, examples, and pitfalls. The Math Functions index is only a catalog—search and open individual guides such as hypot(). Learn here first, then browse the index.

C Syntax

Include the header, call functions, and link the math library:

#include <math.h>
#include <stdio.h>

int main(void) {
    double x = 16.0;
    double root = sqrt(x);
    double power = pow(2.0, 10.0);

    printf("sqrt(16) = %.0f\n", root);
    printf("2^10     = %.0f\n", power);

    return 0;
}
/* gcc math_basics.c -std=c11 -o math_basics -lm */

Core C Concepts

Ideas every C math tutorial builds on:

Type variants

When to use which function

How to Use Math in C

A practical workflow for this tutorial track:

1. Add #include <math.h> (and <stdlib.h> if you need integer abs).
2. Compile with -lm on GCC/Clang; confirm the program links cleanly.
3. Store floating results in double unless you have a reason not to.
4. Convert degrees to radians before calling circular trig functions.
5. Print with printf format specifiers such as %.2f or %g.
6. Open the functions index when you need a specific API guide.

Live Preview

Enter a non-negative number to preview sqrt(x)—the same idea as calling sqrt() after including <math.h>.

C Examples

Five starter patterns from a C tutorial. Compile with gcc file.c -std=c11 -o out -lm.

#include <math.h>
#include <stdio.h>

int main(void) {
    double area = 78.54;
    double radius = sqrt(area / M_PI);

    printf("Area: %.2f\n", area);
    printf("Radius: %.2f\n", radius);

    return 0;
}

Area: 78.54
Radius: 5.00

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int n = -42;
    double x = -3.14159;

    printf("abs(%d)     = %d\n", n, abs(n));
    printf("fabs(%g) = %g\n", x, fabs(x));

    return 0;
}

abs(-42)     = 42
fabs(-3.14159) = 3.14159

#define _USE_MATH_DEFINES
#include <math.h>
#include <stdio.h>

int main(void) {
    double degrees = 45.0;
    double radians = degrees * M_PI / 180.0;
    double result = sin(radians);

    printf("sin(%.0f degrees) = %.6f\n", degrees, result);

    return 0;
}

sin(45 degrees) = 0.707107

#include <math.h>
#include <stdio.h>

int main(void) {
    double a = 3.0;
    double b = 4.0;
    double c = sqrt(pow(a, 2.0) + pow(b, 2.0));

    printf("Sides: %.0f, %.0f\n", a, b);
    printf("Hypotenuse: %.0f\n", c);

    return 0;
}

Sides: 3, 4
Hypotenuse: 5

#include <math.h>
#include <stdio.h>

int main(void) {
    double x = -2.7;

    printf("x = %.1f\n", x);
    printf("floor(x) = %.1f  (toward -infinity)\n", floor(x));
    printf("trunc(x) = %.1f  (toward zero)\n", trunc(x));
    printf("round(x) = %.1f  (nearest integer)\n", round(x));

    return 0;
}

x = -2.7
floor(x) = -3.0  (toward -infinity)
trunc(x) = -2.0  (toward zero)
round(x) = -3.0  (nearest integer)

Where to Go Next

This page teaches how math works in C (math.h, -lm, radians, examples). The full searchable catalog of every function tutorial lives on the Math Functions index—start with these six:

Need ceil, log, atan2, hyperbolic functions, or the rest? Open the complete Math Functions index.

Platform Support

<math.h> is part of standard C. Linking details differ by toolchain.

Core functions such as sqrt, pow, sin, fabs, and floor are portable C99/C11 APIs. Some constants (like M_PI) are common extensions—guard them or define your own PI when portability matters.

Key Takeaways