How Is Golf Handicap Index Calculated? Here's the Formula

Woman golfer putting the ball into the hole
Vichien Petchmai/Getty Images

The golf handicap calculation is something that most golfers never have to worry about. If you carry an official USGA Handicap Index, the calculation is performed for you by other people (or, far more likely, by a computer). You can also get an unofficial estimate of your handicap by using a golf handicap calculator.

But you want the nuts and bolts of the handicap formula, don't you? You want to know the math behind figuring handicaps. OK, you asked for it, you got it.

What You'll Need for the Handicap Formula

What numbers do you have to have in order to perform the handicap index calculation? The formula requires the following:

Have all that? OK, we're ready to get into the math of the handicap formula.

Step 1 In Handicap Formula: Calculate the Differentials

Using your adjusted gross scores, the course ratings, and slope ratings, Step 1 is calculating the handicap differential for each round entered using this formula:

(Score - Course Rating) x 113 / Slope Rating

For example, let's say your score is 85, the course rating 72.2, the slope 131. The formula would be:

(85 - 72.2) x 113 / 131 = 11.04

The sum of that calculation is called your "handicap differential." This differential is calculated for each round entered (minimum of five, maximum of 20).

(Note: The number 113 is a constant and represents the slope rating of a golf course of average difficulty.)

Step 2: Determine How Many Differentials To Use

Not every differential that results from Step 1 will be used in the next step. If only five rounds are entered, only the lowest of your five differentials will be used in the following step. If 20 rounds are entered, only the 10 lowest differentials are used. Use this chart to determine how many differentials to use in your handicap calculation.

Number of Differentials UsedThe number of rounds you are reporting for handicap purposes determines the number of differentials used in the USGA handicap calculation, as follows:
Rounds Entered Differentials Used
5-6 rounds Use 1 lowest differential
7-8 rounds Use 2 lowest differentials
9-10 rounds Use 3 lowest differentials
11-12 rounds Use 4 lowest differentials
13-14 rounds Use 5 lowest differentials
15-16 rounds Use 6 lowest differentials
17 rounds Use 7 lowest differentials
18 rounds Use 8 lowest differentials
19 rounds Use 9 lowest differentials
20 rounds Use 10 lowest differentials

Step 3: Average Your Differentials

Get an average of the differentials used by adding them together and dividing by the number used (i.e., if five differentials are used, add them up and divide by five).

Step 4: Arriving At Your Handicap Index

And the final step is to take the number that results from Step 3 and multiply the result by 0.96 (96-percent). Drop all the digits after the tenths (do not round off) and the result is handicap index.

Or, to combine Steps 3 and 4 into a single formula:

(Sum of differentials / number of differentials) x 0.96

Let's give an example using five differentials. Our differentials worked out to (just making up some numbers for this example) 11.04, 12.33, 9.87, 14.66 and 10.59. So we add those up, which produces the number 58.49. Since we used five differentials, we divide that number by five, which produces 11.698. And we multiply that number by 0.96, which equals 11.23, and 11.2 is our handicap index.

Thankfully, as we said at the beginning, you don't have to do the math on your own. Your golf club's handicap committee will handle it for you, or the GHIN system if you log in to post scores.

Just imagine: Once upon a time, these calculations were all done by hand. Reason to be thankful for computers, right?