Average of Numbers in C

The arithmetic mean is the sum of all values divided by the number of values. In C, use a floating-point calculation when the average may contain a fractional part.

Average of Two Numbers Top ↑

#include <stdio.h>

int main(void) {
    double first = 12.0;
    double second = 15.0;
    double average = (first + second) / 2.0;

    printf("Average = %.2f\n", average);
    return 0;
}

Average of User-Entered Numbers Top ↑

#include <stdio.h>

int main(void) {
    double first;
    double second;

    printf("Enter two numbers: ");
    if (scanf("%lf %lf", &first, &second) != 2) {
        printf("Invalid input.\n");
        return 1;
    }

    printf("Average = %.2f\n", (first + second) / 2.0);
    return 0;
}

Average of an Array Top ↑

#include <stdio.h>

int main(void) {
    double values[] = {10.0, 12.5, 8.5, 14.0};
    size_t count = sizeof values / sizeof values[0];
    double sum = 0.0;

    for (size_t i = 0; i < count; i++) {
        sum += values[i];
    }

    printf("Average = %.2f\n", sum / count);
    return 0;
}

For an array, derive the element count from the array itself instead of hard-coding the divisor.

Preserved Example: Weighted Average Top ↑

The original page included a weighted-average example, which is different from an ordinary arithmetic mean because each value contributes according to its weight.

#include <stdio.h>

int main(void) {
    int values[] = {70, 80, 90};
    int weights[] = {1, 2, 3};
    size_t count = sizeof values / sizeof values[0];
    int weighted_sum = 0;
    int total_weight = 0;

    for (size_t i = 0; i < count; i++) {
        weighted_sum += values[i] * weights[i];
        total_weight += weights[i];
    }

    double weighted_average =
        (double)weighted_sum / total_weight;

    printf("Weighted Average: %.2f\n", weighted_average);
    return 0;
}

Subhendu Mohapatra

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