Baseball stats calculator

The formulas

ERA = earned runs × 9 ÷ innings pitched WHIP = (walks + hits) ÷ innings pitched AVG = H ÷ AB OBP = (H + BB + HBP) ÷ (AB + BB + HBP + SF) SLG = total bases ÷ AB, OPS = OBP + SLG

Innings are written with outs after the point: 186.2 means 186⅔ innings. For a simpler batting-only tool, see the batting average calculator.

How to use the baseball stats calculator

Pick Pitching to get ERA and WHIP or Batting to get batting average, on-base percentage, slugging and OPS. For pitching, enter earned runs, innings pitched, walks and hits allowed. Write innings with the outs after the decimal point, so 186.2 is 186⅔ innings and 180.1 is 180⅓. For batting, enter at-bats, hits, doubles, triples, home runs, walks, hit by pitch and sacrifice flies. The result shows each rate to three decimals (two for ERA) with the working underneath.

The pitching formulas

ERA = earned runs × 9 ÷ innings pitched WHIP = (walks + hits) ÷ innings pitched

ERA is the earned runs a pitcher would allow over nine innings. WHIP is the number of baserunners allowed by walk or hit per inning. Innings use thirds: an out is one third of an inning, so 186.2 means 186.667 when you do the arithmetic. With 62 earned runs, 186⅔ innings, 48 walks and 155 hits, ERA = 62 × 9 ÷ 186.667 = 2.99 and WHIP = 203 ÷ 186.667 = 1.088.

The batting formulas

AVG = H ÷ AB OBP = (H + BB + HBP) ÷ (AB + BB + HBP + SF) SLG = total bases ÷ AB OPS = OBP + SLG total bases = singles + 2×doubles + 3×triples + 4×home runs

Batting average counts only hits per at-bat. On-base percentage includes walks and hit by pitch, so it measures how often a hitter reaches base. Slugging weights extra-base hits, and OPS adds the two together. Walks and hit by pitch do not count as at-bats, and sacrifice flies appear in the OBP denominator but not as hits.

Worked example: a full batting line

A hitter has 540 at-bats, 155 hits (30 doubles, 2 triples, 24 home runs), 48 walks, 4 hit by pitch and 5 sacrifice flies. Singles are 155 − 30 − 2 − 24 = 99, so total bases are 99 + 60 + 6 + 96 = 261. Then AVG = .287, OBP = 207 ÷ 597 = .347, SLG = 261 ÷ 540 = .483 and OPS = .830. An OPS above .800 is generally very good, and .900 or more is star level.

Pitching examples

• One game: 3 earned runs in 6 innings is 3 × 9 ÷ 6 = 4.50 ERA for that game.
• A complete game shutout: 0 earned runs in 9 innings is a 0.00 ERA. Allowing 1 in 9 is 1.00.
• Partial innings: 6.1 innings is 6⅓, which is 6.333 when computing.

Reading the numbers

A starting pitcher with an ERA under 3.50 and a WHIP near 1.15 is usually doing well. Hitters who bat .300 are strong, an OBP of .370 or more is excellent and a slugging percentage above .500 shows real power. What counts as good changes with the league and era, so compare players against the same season and league. Rate stats from a few games swing wildly, so give small samples little weight.

What these stats leave out

ERA depends on the defence behind a pitcher and on how errors and scoring decisions are recorded. Batting average ignores walks, and OPS counts OBP and SLG equally even though a point of OBP is worth more than a point of slugging. Modern analysis adds park factors, strikeouts, fielding-independent measures and win probability. Use these figures to describe a player’s line, not to settle an argument alone.

Quick reference: what the numbers mean

These bands are rough guides for a recent major-league season. Leagues, ages and eras differ, so they are no substitute for comparing against the right group.

Combining a season from game lines

To get season rates, add the counts first and divide once. Never average per-game averages, because a 4-for-4 game then counts the same as a 0-for-1 game. Sum the hits and at-bats from every game and compute the rate from the totals, in the same way for ERA with total earned runs and total innings (in thirds).

Sample-size and league context

A hitter who goes 3 for 10 is batting .300, but ten at-bats say almost nothing about talent; a full season of about 500 at-bats is much more reliable. The same holds for ERA, where a single bad outing of 7 earned runs in 2 innings produces a 31.50 ERA that shrinks fast over a season. When comparing players from different years, look at how they stood relative to the league that season rather than raw numbers alone.

Common mistakes and limits

• Reading 186.2 as 186.2 innings. The digit after the point is outs, not tenths.
• Counting walks as at-bats. Walks and hit by pitch are plate appearances but not at-bats.
• Using all runs instead of earned runs. ERA counts earned runs only.
• Entering hits as only singles. Hits include doubles, triples and home runs.