Batting Average Calculator

The formula: hits ÷ at-bats, rounded at the fourth decimal

Official Baseball Rule 9.21(b) defines batting average as safe hits divided by times at bat as defined in rule 9.02(a). A double or a home run still counts as one hit — that is what separates average from slugging percentage, which counts total bases.

Averages are shown to three decimals. NPB and KBO state the method explicitly: work out four decimals, then round. So 161 ÷ 502 = .32071… becomes .3207 and then .321, and 1-for-2,000 (.0005) rounds up to .001. The calculator uses integer math so no floating-point error creeps in.

• 161-for-502 → .3207 → .321
• 165-for-440 → .3750 → .375
• 5-for-12 → .4167 → .417
• 1-for-2,001 → below .0005 → .000

At-bats versus plate appearances

A plate appearance is every completed trip to the plate; an at-bat is the subset that counts toward average. Rule 9.02(a)(1) removes these from at-bats:

• Walks (base on balls)
• Hit by pitch
• Sacrifice bunts and sacrifice flies
• Reaching first on catcher's interference or obstruction

Counting at-bats from a scorebook

Five trips to the plate with a walk, a sacrifice fly, a single and two outs is a 1-for-3 day. Dividing by the five plate appearances would give .200, but the average uses 1 ÷ 3.

Reaching on an error, on the other hand, is an at-bat without a hit, so it lowers the average. Those two cases are easy to get wrong when rec-league or youth scorebooks are copied into a spreadsheet.

Reading an average out loud

Averages drop the leading zero and are spoken like a number: .321 is "three twenty-one," .300 is "three hundred," .250 is "two fifty." A change of .001 is one point, so going from .318 to .326 is "up eight points."

Two averages that match at three decimals can still differ. The Team tab ranks players by the unrounded ratio and, when the displayed averages are equal, shows a fourth decimal cut short, such as .3001….

• .321three twenty-one
• .305three oh five
• .250two fifty
• 1.000a thousand

Qualified plate appearances: each league rounds differently

The batting, on-base and slugging titles go to the best hitter among those with enough plate appearances. The base is 3.1 per game everywhere, but leagues count games and handle the fraction differently.

The gap shows up when the fraction is .5 or more. A 145-game schedule gives 449.5: NPB rounds up to 450 and KBO drops to 449. The MLB rule does not say what to do with an exact .5, so the calculator rounds it up like NPB and prints the value it used on the rule line.

Mid-season, type the games your team has played to see today's line. For minor leagues that use 2.7 per game or for a rec league with its own rule, choose Custom and set the multiplier and the rounding.

• MLBScheduled games × 3.1, nearest whole number — 162 G: 502.2 → 502 PA
• NPBGames played × 3.1, rounded half up — 143 G: 443.3 → 443 PA
• KBOGames played × 3.1, fraction dropped — 144 G: 446.4 → 446 PA

Winning the title without enough plate appearances

Rule 9.22(a) has an exception: charge the missing plate appearances as hitless at-bats, and if the hitter still leads, the title is his. The average that goes into the record book is the real one, before the added at-bats.

The rule's own example: the best qualified hitter is 181-for-500 (.362). A player with 490 plate appearances and 165-for-440 (.375) is 12 short; 165 ÷ 452 = .365 still leads, so he wins the title at .375.

Enter plate appearances on the Season tab and the calculator shows how many are missing and the adjusted average.

How far one game can move an average

An 0-for-4 barely moves a full-season average but can wreck an early one. The next-game table adds 3, 4 or 5 at-bats to your line and lists the average and the change in points for every hit total.

Changes are measured between the rounded averages shown on screen — the same way a broadcast says a hitter "dropped three points."

• 161-for-502 (.321), then 0-for-4.318, down 3 points
• 161-for-502, then 4-for-4.326, up 5 points
• 5-for-12 (.417), then 0-for-4.313, down 104 points

Hits to .300 — and how long .300 lasts

For each mark (.250, .300, .350, .400) the calculator shows either how many hitless at-bats you can absorb while staying at or above it, or how many straight hits it takes to get there.

The check uses the unrounded average. A 161-for-502 hitter stays at .300 through 34 hitless at-bats; the 35th makes it 161 ÷ 537 = .2998, which still reads .300 on the scoreboard but is below it. Reaching .350 takes 23 straight hits (184 ÷ 525 = .3505).

Walks, hit-by-pitches and sacrifices do not change the average, so the count only includes official at-bats: every one of them is either a hit or an out.

Tracking a season game by game

The Game log tab keeps one row per game. Each row shows the running average after that game and the change, and the chart below draws the whole path. Quick entry takes lines like "4-2 3-0 4-1" (at-bats first) or the familiar "2-for-4."

The log is stored only in this browser and is never sent anywhere. To move it to another device, copy the results; the table pastes into a spreadsheet as columns.

• Last 5 and last 10 games: hits and at-bats of the most recent games, re-added into one average
• Multi-hit games: two or more hits
• Hitless games: at least one at-bat and no hit
• Best game: most hits, then fewest at-bats

When a hitting streak ends

Under rule 9.23(b), a consecutive-game hitting streak survives a game in which every plate appearance is a walk, hit by pitch, interference or sacrifice bunt. A sacrifice fly with no hit ends it.

Because the calculator only knows at-bats and hits, it treats a 0-AB game as one that keeps the streak alive. If that game was really a sacrifice fly and nothing else, count the streak as broken there.

For example, in the log 4-2, 3-0, 4-1, 0-0, 5-3, 4-0, the longest streak is two games (games 3 and 5, with game 4 skipped), and the final 0-for-4 resets it to zero. The running average starts at .500 and ends at .300.

Team average is not the mean of player averages

Team batting average is total team hits divided by total team at-bats. Averaging the players' averages gives a bench player with 40 at-bats the same weight as an everyday starter.

The Team tab shows both numbers side by side. Set a minimum at-bat count and small samples drop below the ranking while still counting toward the team total.

• A: 120-for-400.300
• B: 20-for-40.500
• C: 98-for-350.280
• Team: 238 ÷ 790.301
• Mean of the three averages.360

What batting average leaves out

Average ignores walks and treats a single like a home run. Two .300 hitters can be very different: one walks a lot and has a high on-base percentage, the other hits for power and slugs higher. Around 100 at-bats, a handful of hits can reshuffle a leaderboard.

Results here are arithmetic on the numbers you enter, not official statistics. Where a league's official record or tournament rules differ, those govern.

• Getting on base: on-base percentage (OBP)
• Power: slugging (SLG) and ISO
• Both together: OPS
• Results on balls in play: BABIP