Batting Average, OBP, SLG & OPS Calculator

Understanding the batting average, OBP, SLG and OPS calculator — concept and principle

These four rate statistics are the standard way to describe a hitter. Batting average (AVG) measures how often a hitter gets a hit, on-base percentage (OBP) how often he reaches base, slugging percentage (SLG) how much power each at-bat produces, and OPS adds OBP and SLG into one quick summary. Isolated power (ISO) is also shown.

Singles to home runs count 1–4 bases; OBP + SLG gives OPS .929.

How it is calculated

H = 1B + 2B + 3B + HR; total bases TB = 1B + 2 × 2B + 3 × 3B + 4 × HR.
AVG = H / AB.
OBP = (H + BB + HBP) / (AB + BB + HBP + SF).
SLG = TB / AB.
OPS = OBP + SLG.
ISO = SLG − AVG, the extra bases per at-bat beyond singles.

At-bats exclude walks, hit-by-pitches, sacrifice flies and sacrifice bunts, which is why OBP adds BB, HBP and SF back into its denominator.

The principle

AVG treats every hit the same and ignores walks, so it misses two things that create runs: reaching base without a hit and hitting for extra bases. OBP fixes the first, because avoiding outs is the most valuable thing a hitter does. SLG fixes the second by weighting each hit by the bases it gains. OPS is popular because it correlates well with team run scoring and is easy to compute, even though it is a sum of two ratios with different denominators and gives OBP slightly less weight than it deserves.

Worked example

Inputs: 500 AB, 100 singles, 30 doubles, 3 triples, 25 HR, 60 BB, 5 HBP, 5 SF.
H = 100 + 30 + 3 + 25 = 158; AVG = 158 / 500 = .316.
OBP = (158 + 60 + 5) / (500 + 60 + 5 + 5) = 223 / 570 = .3912.
TB = 100 + 60 + 9 + 100 = 269; SLG = 269 / 500 = .538.
OPS = 0.39123 + 0.538 = .9292; ISO = .538 − .316 = .222.

Each point is the calculator re-run with only “At bats” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

At bats	OPS
125	3.295589744
250	1.772875
375	1.218456929
500	0.9292280702
625	0.7512633094
750	0.6306178862
1,000	0.477411215

How to read the result

In recent MLB seasons, league averages have been roughly .245 AVG, .315 OBP, .400–.415 SLG and an OPS of about .710–.735. As a rough guide, an OPS of .800 is clearly above average, .900 is excellent and 1.000 is elite. An ISO above .200 marks a power hitter. This example, a .929 OPS with 25 home runs, would rank among the better hitters in a typical season.

Common mistakes

Using plate appearances instead of at-bats for AVG and SLG.
Counting a home run as one base in TB instead of four.
Comparing OPS across eras or ballparks without adjustment; OPS+ normalises for league and park.

Keep in mind: These are descriptive statistics. Small samples (a few weeks) swing widely, and park and league environment matter, so compare like with like.

Frequently asked questions

Does reaching on an error count for OBP?

No. Errors and fielder's choices count as at-bats without reaching base for OBP.

Why is sacrifice bunt not in OBP?

By rule, sacrifice bunts are excluded from OBP's denominator, while sacrifice flies are included.

Is OPS better than batting average?

Yes for predicting runs, but wOBA weights each event more accurately than OPS.

Sources: Official Baseball Rules, Office of the Commissioner of Baseball (percentage records) · MLB.com Glossary, OBP, SLG and OPS

Checked 8 Nov 2026. Official league / federation formulas where they exist; widely used community formulas otherwise. For fun and analysis — not betting advice.

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