Baseball · Calculator
Earned-run average is defined in the Official Baseball Rules; WHIP, the per-nine rates and the strikeout-to-walk ratio are the statistics usually printed beside it. All of them are scaled to innings, and innings are where most hand calculations go wrong: 6.1 innings in a box score means six and one-third, not six and one-tenth.
This calculator takes innings the way box scores write them, can scale ERA to a shorter regulation game, and adds fielding independent pitching when you supply — or work out — the season’s constant.
By Reign Creative LLCPublished More in the Baseball hub
Enter innings as a box score prints them: 6.1 is six innings and one out.
Earned-run average (ERA)3.09per nine innings
180.2 innings is 542 outs, or 180.667 innings as a decimal. Add a FIP constant above to calculate FIP.
Every one of these statistics divides by innings pitched, and box scores do not write innings as decimals. Each out is a third of an inning, so the digit after the point counts outs and can only be 0, 1 or 2:
| Written | Outs | Innings as a decimal |
|---|---|---|
| 6.0 | 18 | 6.000 |
| 6.1 | 19 | 6.333 |
| 6.2 | 20 | 6.667 |
Dividing by 6.1 instead of 6.333 is the most common way a hand-calculated ERA comes out wrong. The calculator converts first and rejects 6.3, which cannot occur.
Earned-run average (Rule 9.21(e))
ERA = earned runs × 9 ÷ innings pitched
Walks plus hits per inning pitched
WHIP = (walks + hits) ÷ innings pitched
Per nine innings
K/9, BB/9, HR/9 = count × 9 ÷ innings pitched
Strikeout-to-walk ratio
K/BB = strikeouts ÷ walks
Fielding independent pitching
FIP = (13 × HR + 3 × (BB + HBP) − 2 × K) ÷ IP + constant
FIP constant (FanGraphs)
constant = league ERA − (13 × lgHR + 3 × (lgBB + lgHBP) − 2 × lgK) ÷ league IP
ERA and WHIP describe what happened while the pitcher was on the mound, fielders included. The per-nine rates, K/BB and FIP lean on the outcomes a pitcher controls most directly. The constant only puts FIP on the same scale as the league’s ERA for a season: applied to the league’s own totals, it returns the league ERA.
The rulebook’s own example: 3 earned runs in 9⅓ innings is an ERA of 2.89 — 3 × 9 = 27, divided by 9.333.
A fuller, illustrative season — not a real pitcher — of 180.2 innings, 62 earned runs, 160 hits, 50 walks, 190 strikeouts, 20 home runs and 6 hit batters, with a FIP constant of 3.10 — the figure FanGraphs describes as typical, used here only for illustration:
| Statistic | Calculation | Result |
|---|---|---|
| ERA | 62 × 9 ÷ 180.667 | 3.09 |
| WHIP | (50 + 160) ÷ 180.667 | 1.16 |
| K/9 | 190 × 9 ÷ 180.667 | 9.5 |
| BB/9 | 50 × 9 ÷ 180.667 | 2.5 |
| HR/9 | 20 × 9 ÷ 180.667 | 1.0 |
| K/BB | 190 ÷ 50 | 3.80 |
| FIP | (260 + 168 − 380) ÷ 180.667 + 3.10 | 3.37 |
In a league with seven-inning games, the same arithmetic uses seven: 7 earned runs in 21.0 innings is 3.00 per nine innings but 2.33 per seven-inning game. Neither number is wrong; they are on different scales, so compare pitchers only on the same one.
The ERA explainer and the WHIP explainer go into where each number misleads.
162-0 Baseball Draft & GM Team compares pitchers on ERA and WHIP, among other numbers, before you draft them, and its Franchise GM Mode has you manage the rotation and bullpen.
Reign Creative LLC makes 162-0 Baseball Draft & GM Team, so we have a commercial interest in it. It is not affiliated with, or endorsed by, any league, team, players’ association or athlete.
Good to know
League, governing-body and team names appear here only to identify the formulas and rules being used. Reign Creative LLC's sports games and calculators are not affiliated with, endorsed by or licensed by any league, team, players' association or athlete, and all names and marks belong to their owners.
ERA charges a pitcher for his fielders, his luck and the order of events. FIP rebuilds it from the outcomes he controls. How it works, and when ERA still wins.
How earned run average is calculated, what counts as an earned run, why ERA flatters some pitchers, and how to read it in a simulated season.
Walks and hits per inning pitched: how WHIP is calculated, what it captures that ERA misses, and what it deliberately ignores.
What each pitching role actually does, how workload and leverage differ, and why a bullpen is built the way it is — with the simulation consequences of each.
ERA, WHIP, OBP, slugging, fielding percentage and WAR, each with the formula and a worked example, plus what every one of them fails to tell you.
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