Component ERA
Open-knowledge reference entry
Component ERA or ERC is a baseball statistic invented by Bill James. It attempts to forecast a pitcher's earned run average (ERA) from the number of hits and walks allowed rather than the standard formula of average number of earned runs per nine innings. ERC allows one to take a fresh look at a pitcher's performance and gauge if his results are more or less than the sum of its parts.
The formula for ERC as it appears in the 2004 edition of the Bill James Handbook:
E
R
C
=
9
∗
(
H
+
B
B
+
H
B
P
)
∗
P
T
B
B
F
P
∗
I
P
−
0.56
{\displaystyle ERC=9*{(H+BB+HBP)*PTB \over BFP*IP}-0.56}
where H is hits, BB is bases on balls (walks), HBP is hit by pitch, BFP is batters faced by pitcher, IP is innings pitched, and PTB is pitcher's total bases and is defined as:
P
T
B
=
0.89
∗
(
1.255
∗
(
H
−
H
R
)
+
4
∗
H
R
)
+
0.56
∗
(
B
B
+
H
B
P
−
I
B
B
)
{\displaystyle PTB=0.89*(1.255*(H-HR)+4*HR)+0.56*(BB+HBP-IBB)}
where HR is home runs, IBB is intentional walks, and others are as above.
The point of the first component is to represent the number of baserunners allowed. The PTB component combines an estimate of extra bases allowed (first half) with the fact that walks and hit by pitches do not advance unforced baserunners (second half). The division places the computation into an ERA context, and the final subtraction moves that scale down into its normal range.
Where intentional walk data are not available use:
P
T
B
=
0.89
∗
(
1.255
∗
(
H
−
H
R
)
+
4
∗
H
R
)
+
0.475
∗
(
B
B
+
H
B
P
)
{\displaystyle PTB=0.89*(1.255*(H-HR)+4*HR)+0.475*(BB+HBP)}
If ERC is less than 2.24, the formula is adjusted as follows:
E
R
C
=
9
∗
(
H
+
B
B
+
H
B
P
)
∗
P
T
B
B
F
P
∗
I
P
∗
0.75
{\displaystyle ERC=9*{(H+BB+HBP)*PTB \over BFP*IP}*0.75}
Other people and organizations have their own proprietary formulae for ERC which may correlate more highly with actual earned runs scored than the formula above.
Component ERA was added to the ESPN.com "Sortable Stats" in 2004.
See also
Earned Run Average
DIPS
WHIP
References
James, Bill (2007).
Begin with the source’s own compact description: “Component ERA” is open-knowledge reference entry. The dossier treats that line as a proposition to test through Component, Open-knowledge and entry, not as a finished interpretation.
Why this record matters
The phrase “open-knowledge reference entry” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jul 1, 2025. The linked authority identifier is Q5156689. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2004 and 2007.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Component ERA”, its source revision and the description used here.
- Expand the search: follow Component ERA primary sources, Component ERA archive and Component research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Component ERA”?
- Which institution is responsible for the underlying evidence?
- Which cited source is closest to the event, object or claim?
Search terms from this dossier
This entry incorporates text from “Component ERA” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.