BAA Calculator

Batting average against (BAA, sometimes Opp AVG) is hits allowed divided by at-bats against. It is the mirror image of a hitter's batting average — how opponents hit when this pitcher is on the mound.

Walks, hit batters and sacrifice bunts/flies are not at-bats, so they don't appear in the denominator. A pitcher who walks many batters can still post a low BAA while allowing plenty of traffic.

The result is usually written without a leading zero when it's below 1.000 — for example .245 instead of 0.245 — just like batting average.

1. Total hits allowed.
2. Total at-bats against (official AB, not plate appearances).
3. Confirm hits do not exceed at-bats.
4. Divide hits by at-bats and round to three decimal places.

Worked example

98 hits in 400 at-bats against is 98 ÷ 400 = .245 BAA.

H/9 rates hits per nine innings. WHIP adds walks to hits and divides by innings. BAA asks only how often balls put in play (plus reaching on hits within AB) became hits relative to at-bats. Use all three when you care about contact, walks and workload together.