C++ Grade Calculator: Build One Step by Step
A grade calculator is an excellent beginner project — it uses variables, loops, arrays or vectors, functions, and conditionals all in one program. This tutorial builds one from scratch, adding features at each step.
Version 1: Fixed Number of Scores
The simplest version — ask for exactly 5 scores and compute the average and grade:
#include <iostream>
using namespace std;
char getLetterGrade(double average) {
if (average >= 90) return 'A';
if (average >= 80) return 'B';
if (average >= 70) return 'C';
if (average >= 60) return 'D';
return 'F';
}
int main() {
const int NUM_SCORES = 5;
double scores[NUM_SCORES];
double total = 0;
cout << "Enter " << NUM_SCORES << " scores:\n";
for (int i = 0; i < NUM_SCORES; i++) {
cout << "Score " << (i + 1) << ": ";
cin >> scores[i];
total += scores[i];
}
double average = total / NUM_SCORES;
char grade = getLetterGrade(average);
cout << "\nAverage: " << average << "\n";
cout << "Grade: " << grade << "\n";
return 0;
}Sample output:
Enter 5 scores:
Score 1: 85
Score 2: 92
Score 3: 78
Score 4: 90
Score 5: 88
Average: 86.6
Grade: BVersion 2: Any Number of Scores Using a Vector
More flexible — uses a vector so you can enter as many scores as you like:
#include <iostream>
#include <vector>
#include <numeric> // for accumulate
using namespace std;
char getLetterGrade(double avg) {
if (avg >= 90) return 'A';
if (avg >= 80) return 'B';
if (avg >= 70) return 'C';
if (avg >= 60) return 'D';
return 'F';
}
string getGradeDescription(char grade) {
switch (grade) {
case 'A': return "Excellent";
case 'B': return "Good";
case 'C': return "Average";
case 'D': return "Below Average";
default: return "Failing";
}
}
int main() {
vector<double> scores;
double score;
cout << "Enter scores one at a time. Type -1 to finish.\n";
while (true) {
cout << "Score: ";
cin >> score;
if (score == -1) break;
if (score < 0 || score > 100) {
cout << "Invalid score. Enter a value between 0 and 100.\n";
continue;
}
scores.push_back(score);
}
if (scores.empty()) {
cout << "No scores entered.\n";
return 0;
}
double total = 0;
for (double s : scores) total += s;
double average = total / scores.size();
char grade = getLetterGrade(average);
cout << "\n=== Grade Report ===\n";
cout << "Scores entered: " << scores.size() << "\n";
cout << "Average: " << average << "\n";
cout << "Grade: " << grade << " (" << getGradeDescription(grade) << ")\n";
return 0;
}This version validates input, handles any number of scores, and gives a description with the grade.
Version 3: Full Report with Statistics
A more complete version that adds highest score, lowest score, and shows each score with its individual letter grade:
#include <iostream>
#include <vector>
#include <algorithm> // min_element, max_element
#include <iomanip> // setprecision, fixed
using namespace std;
char letterGrade(double score) {
if (score >= 90) return 'A';
if (score >= 80) return 'B';
if (score >= 70) return 'C';
if (score >= 60) return 'D';
return 'F';
}
int main() {
int n;
cout << "How many scores? ";
cin >> n;
if (n <= 0) {
cout << "Must enter at least one score.\n";
return 1;
}
vector<double> scores(n);
for (int i = 0; i < n; i++) {
cout << "Score " << (i + 1) << " (0-100): ";
cin >> scores[i];
}
// Calculate stats
double total = 0;
for (double s : scores) total += s;
double average = total / n;
double highest = *max_element(scores.begin(), scores.end());
double lowest = *min_element(scores.begin(), scores.end());
// Print report
cout << fixed << setprecision(1);
cout << "\n======= Grade Report =======\n";
cout << left << setw(10) << "Score" << setw(8) << "Grade" << "\n";
cout << "----------------------------\n";
for (int i = 0; i < n; i++) {
cout << setw(10) << scores[i] << setw(8) << letterGrade(scores[i]) << "\n";
}
cout << "----------------------------\n";
cout << "Average: " << average << " (" << letterGrade(average) << ")\n";
cout << "Highest: " << highest << "\n";
cout << "Lowest: " << lowest << "\n";
return 0;
}Sample output for 4 scores (85, 92, 73, 68):
======= Grade Report =======
Score Grade
----------------------------
85.0 B
92.0 A
73.0 C
68.0 D
----------------------------
Average: 79.5 (C)
Highest: 92.0
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Weighted Grade Calculator
Many courses weight exams, homework, and participation differently:
#include <iostream>
using namespace std;
int main() {
double homework, midterm, finalExam;
double hwWeight = 0.30, midWeight = 0.30, finalWeight = 0.40;
cout << "Homework score (0-100): ";
cin >> homework;
cout << "Midterm score (0-100): ";
cin >> midterm;
cout << "Final exam score (0-100): ";
cin >> finalExam;
double weighted = (homework * hwWeight)
+ (midterm * midWeight)
+ (finalExam * finalWeight);
char grade;
if (weighted >= 90) grade = 'A';
else if (weighted >= 80) grade = 'B';
else if (weighted >= 70) grade = 'C';
else if (weighted >= 60) grade = 'D';
else grade = 'F';
cout << "\nWeighted average: " << weighted << "\n";
cout << "Final grade: " << grade << "\n";
return 0;
}Key Concepts Used
vector<double>— stores variable number of scores- Range-based for loop — iterates over all scores cleanly
max_element/min_element— from<algorithm>, finds highest/lowestsetprecision/fixed— formats decimal output- Functions —
letterGrade()separates grading logic from I/O - Input validation — rejects scores outside 0-100
Related Articles
- C++ Variables and Data Types — types used in the calculator
- C++ Loops Tutorial — for loops and range-based for
- C++ Vector Tutorial — using vectors to store scores
- C++ Functions Tutorial — organizing code into functions
- C++ Calculator Program — another beginner project
Take Your C++ Further
If you’re looking to go deeper with C++, the C++ Better Explained Ebook is perfect for you — whether you’re a complete beginner or looking to solidify your understanding. Just $19.