how to convert float to close it number in (int)

Question

float index = 0.0588 * L - 0.296 * S - 15.8;
int i = index;
printf("%i",i);

1. //index equal 11.706415

2. //when I convert the index to int the int will equal 11 "I want it to be 12"

Answer 1

Your existing code rounds toward zero, also known as integer truncation. You appear to what some form of round to nearest, but you didn't specify which.

---

In this particular case, you can use

printf( "%.0f", index );

By default, this rounds to nearest, half to even.

---

This rounds to nearest, half away from zero.

#include <math.h>   // Also need to link math lib (e.g. using -lm)

int i = lroundf( index );

---

This rounds to nearest, half up.

int i = index + 0.5;

---

input	round to nearest half to even	round to nearest half away from zero	round to nearest half up
-7.5	-8	-8	-7
-6.5	-6	-7	-6
+6.5	+6	+7	+7
+7.5	+8	+8	+8

Answer 2

When you cast a float to an int it will be truncated. You can use roundf() then cast the return value to an int:

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

int main(void) {
    float index = 11.706415;
    printf("truncated: %d\n"
           "rounded:   %d\n",
           (int) index,
           (int) roundf(index));
}