Your handicap is the average of your best 8 score differentials from your last 20 rounds. A differential measures how a round went compared with how hard the course was:
With fewer than 20 rounds, you average fewer of your best ones. You need at least 3 rounds to start.
Step 1: Adjust your score
A handicap shows what you can do on a good day, so one disaster hole shouldn't count in full. Each hole is capped before you add up your score:
- Once you have a handicap: the most a hole can count for is net double bogey, which is par plus 2 plus any strokes you get on that hole.
- For your first rounds: the most a hole can count for is par plus 5.
Most rounds need no adjustment. If you made a 9 on a par 4 and get one stroke there, it counts as a 7. More in our guide to net double bogey.
Step 2: Find the course rating and slope
Every set of tees has two numbers, usually printed on the scorecard next to the tee colors. Course rating is what a scratch golfer should shoot from those tees, like 71.3. Slope says how much harder the course plays for an average golfer, where 113 is standard. See course rating and slope explained.
Step 3: Work out each round's differential
You shoot an adjusted 92 from the Blue tees at Delray Beach Golf Club. Those tees are rated 69.6 with a slope of 111.
That round's differential is 22.8.
The official system also subtracts a small playing-conditions adjustment on days when scores run unusually high or low. It is usually zero, so most calculators leave it out.
Step 4: Average your best differentials
With 20 or more rounds, average your best 8 of the last 20. With fewer, use this table from the Rules of Handicapping:
| Rounds you have | Best ones averaged | Then adjust by |
|---|---|---|
| 3 | 1 | −2.0 |
| 4 | 1 | −1.0 |
| 5 | 1 | none |
| 6 | 2 | −1.0 |
| 7 or 8 | 2 | none |
| 9 to 11 | 3 | none |
| 12 to 14 | 4 | none |
| 15 or 16 | 5 | none |
| 17 or 18 | 6 | none |
| 19 | 7 | none |
| 20 | 8 | none |
Round the result to one decimal place. That's your handicap index. The highest possible is 54.0.
Bonus: how many strokes you get today
Your handicap index is the same everywhere. Your course handicap is how many strokes you get from a particular set of tees:
With a 16.7 index on those same Blue tees (rating 69.6, slope 111, par 72):
You get 14 strokes.
What an official handicap adds
The official system adds two safeguards a home calculation usually skips. It limits how fast your index can rise in a bad stretch, and it trims your index after an exceptional round, one 7 or more strokes better than your index. If you only need a number for casual games, the four steps above get you very close.