C Math Functions

What You’ll Find Here

The C standard library provides powerful math functions in <math.h> for roots, powers, logarithms, trigonometry, rounding, and floating-point decomposition. This page is your central hub: browse all 30 functions in our tutorial series, jump to full guides with five examples each, and learn patterns that work in real C programs.

Introduction

In C, you perform floating-point math through library functions in <math.h> such as sqrt(), pow(), sin(), and floor()—not operators like x^2 in some other languages. Most return double; variants like sqrtf() and sinf() work with float.

Integer absolute value abs() lives in <stdlib.h>, while fabs() handles floating-point magnitudes in <math.h>. Know which header each function needs before you compile.

🚀 Usage Tips

• Link with -lm — on GCC/Clang: gcc file.c -std=c11 -o out -lm.
• Use radians for trig — convert degrees: rad = deg * M_PI / 180.0.
• Pick the right abs — abs() for int, fabs() for double.
• Compare rounding functions — floor, ceil, round, and trunc differ on negatives and halves.
• Prefer atan2 over atan — atan2(y, x) handles all quadrants for slope angles.
• Read the tutorial — each linked page includes syntax, five examples, a quick reference table, and FAQs.

📝 How to Call a Math Function

Every math.h function follows the same general pattern:

#include <math.h>
double result = function_name(arguments);

Common Patterns

math.h vs stdlib.h

Not every numeric helper lives in <math.h>. Integer abs(), labs(), and llabs() are declared in <stdlib.h>. Floating-point math—roots, trig, rounding, fabs()—comes from <math.h>.

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

int main(void) {
    int n = -42;
    double x = -3.14;

    printf("abs(%d)  = %d\n", n, abs(n));
    printf("fabs(%g) = %g\n", x, fabs(x));
    printf("sqrt(16) = %g\n", sqrt(16.0));

    return 0;
}
/* Compile: gcc demo.c -std=c11 -o demo -lm */