A golf handicap allows players of different abilities to compete on a fair basis. Under the World Handicap System (WHS), the primary metric is the Handicap Differential. This number represents the difficulty of your specific round relative to the course difficulty.
The Mathematical Formula
To calculate a single round's handicap differential, use the following formula:
Adjusted Gross Score: Your total strokes minus any adjustments (like Net Double Bogey limits) for the round.
Course Rating: A number (usually between 67 and 77) representing the expected score for a "scratch" golfer.
Slope Rating: A number (between 55 and 155) representing the relative difficulty for a "bogey" golfer compared to a scratch golfer. The average slope is 113.
Calculation Example
If you shot an 88 on a course with a 70.5 rating and a 128 slope:
Step
Calculation
Result
1. Subtract Rating
88 – 70.5
17.5
2. Divide by Slope
113 / 128
0.8828
3. Multiply
17.5 × 0.8828
15.4
Your Handicap Index is eventually calculated by taking the average of your best 8 differentials from your last 20 recorded rounds.
function calculateGolfHandicap() {
var score = document.getElementById('adjustedScore').value;
var rating = document.getElementById('courseRating').value;
var slope = document.getElementById('slopeRating').value;
var resultDiv = document.getElementById('golf-result-area');
if (!score || !rating || !slope || score <= 0 || rating <= 0 || slope <= 0) {
resultDiv.style.display = 'block';
resultDiv.className = 'res-error';
resultDiv.innerHTML = 'Error: Please enter valid positive numbers for all fields.';
return;
}
var scoreVal = parseFloat(score);
var ratingVal = parseFloat(rating);
var slopeVal = parseFloat(slope);
// WHS Formula: (Score – Course Rating) * (113 / Slope Rating)
var differential = (scoreVal – ratingVal) * (113 / slopeVal);
var finalResult = differential.toFixed(1);
resultDiv.style.display = 'block';
resultDiv.className = 'res-success';
var feedback = "";
if (finalResult < 0) {
feedback = " – That's a performance better than a scratch golfer!";
} else if (finalResult <= 10) {
feedback = " – Excellent round!";
} else if (finalResult <= 20) {
feedback = " – Solid mid-handicap performance.";
}
resultDiv.innerHTML = 'Handicap Differential: ' + finalResult + '' + feedback;
}