Baseball and golf both boil a season into a few numbers. Each number answers a narrower question than it seems to. Here is what each one measures, where it misleads, and how one game or one round moves it.
MLB’s glossary defines batting average as hits divided by at-bats. On-base percentage counts how often a batter reaches base per plate appearance: (hits + walks + hit-by-pitch) ÷ (at-bats + walks + hit-by-pitch + sacrifice flies), leaving out errors, fielder’s choices and dropped third strikes. Slugging percentage is total bases per at-bat, (1B + 2×2B + 3×3B + 4×HR) ÷ AB, and it ignores walks. OPS adds OBP and SLG into one number for reaching base and hitting for power.
The three numbers disagree on purpose. Two hitters with 500 at-bats:
| Hitter | AVG | OBP | SLG | OPS |
|---|---|---|---|---|
| Contact hitter | .340 | .378 | .440 | .818 |
| Power and walks | .240 | .362 | .534 | .896 |
The contact hitter (170 hits, 5 homers, 30 walks) wins on average by 100 points. The power hitter (120 hits, 40 homers, 90 walks) nearly matches his on-base percentage and finishes well ahead in OPS. Average alone hides both walks and power. Enter any line in the baseball stats calculator.
A 3-for-4 game lifts a .250 hitter with 40 at-bats to 13 for 44, .295. The same game for a .300 hitter with 500 at-bats moves him to 153 for 504, .304. Early-season averages swing on single games, which is why rate stats need a large sample before they mean much.
MLB defines ERA as 9 × earned runs ÷ innings pitched, where earned runs exclude runs that scored with the help of an error or passed ball. WHIP is walks plus hits per inning; hit batters, errors and fielder’s choices do not count against it. Box scores write partial innings as .1 and .2 for one and two outs, so 180.1 innings is 180⅓: 60 earned runs over 180⅓ innings is a 2.99 ERA. MLB’s glossary also notes that relievers, who often pitch only fractions of an inning, can see their ERA strongly affected by how other relievers pitch.
The World Handicap System, used by the USGA since 2020, starts with a score differential for each round: (adjusted gross score − course rating) × 113 ÷ slope rating. Adjusted gross score caps each hole at net double bogey, double bogey plus any handicap strokes on that hole. A Handicap Index is the average of the best 8 differentials among your most recent 20; the old 0.96 multiplier is gone. You get an Index once you have posted 54 holes, it updates daily, and the maximum is 54.0.
Take a golfer with a 11.2 Index from 20 differentials whose best eight are 9.8 to 12.4. A round with a 4.0 differential pushes out the oldest score (an 11.5, itself one of the best eight) and takes its place, bringing the average of the best eight to 10.3. Because 4.0 is 7.2 strokes better than the 11.2 Index, the exceptional score reduction also applies: 7.0 to 9.9 strokes better takes 1.0 off, 10.0 or more takes 2.0. The new Index is 9.3. Going the other way, the soft cap halves any rise more than 3.0 strokes above the golfer’s lowest Index of the past year, and the hard cap stops it at 5.0.
The USGA formula is Course Handicap = Handicap Index × (slope rating ÷ 113) + (course rating − par). An 11.2 Index on tees rated 71.8 with slope 130 at par 72 gets 11.2 × 130 ÷ 113 − 0.2 = 12.68 strokes, rounded to 13; on forward tees rated 68.0, slope 113, it is 7.20, rounded to 7. Competitions then apply a handicap allowance to get a playing handicap. Run your own differentials in the golf handicap calculator. Bowling leagues solve the same problem differently: handicap is a percentage of the gap between a basis score and your average, so at 90% of 220 a 150 average gets 63 pins a game. The bowling score calculator scores a game frame by frame and works out that allowance.
| Number | Answers | Misses |
|---|---|---|
| Batting average | How often an at-bat ends in a hit | Walks, power |
| OBP | How often a batter reaches base | Extra bases |
| SLG / OPS | Power, and power plus on-base | Speed, defense, park and league scoring level |
| ERA | Earned runs allowed per nine innings | Defense behind the pitcher; small samples for relievers |
| Handicap Index | Demonstrated ability on a standard course | Average round (it uses the best 8 of 20) |
| Course Handicap | Strokes on specific tees | Competition allowances |
The Handicap Index is built from your better rounds, so a typical round usually scores a few strokes above it. That is by design, not a sign that the Index is wrong.
Batting average counts only hits per at-bat. OBP adds walks and hit-by-pitches and divides by plate appearances (minus sacrifice bunts), so it measures how often a batter reaches base.
On-base percentage plus slugging percentage: a .377 OBP and a .522 SLG give an .899 OPS.
180 innings and one out, or 180⅓ innings.
Average the best 8 of your most recent 20 score differentials, where each differential is (adjusted gross score − course rating) × 113 ÷ slope.
A differential 7.0 or more strokes better than your Index triggers an exceptional score reduction of 1.0 or 2.0 strokes, on top of the low score entering your best eight.