On-Base Percentage Calculator
On-base percentage counts every way a hitter reaches base — hits, walks, and hit-by-pitches — over their total plate appearances. It's the single best quick measure of a hitter.
How it works
OBP = (H + BB + HBP) ÷ (AB + BB + HBP + SF). Every time on base counts in the numerator; every plate appearance except a sacrifice bunt counts in the denominator. Reaching on an error or a fielder's choice does not count as reaching base for OBP.
Worked example
With 45 hits, 20 walks, 3 hit-by-pitches, 160 at-bats, and 2 sacrifice flies: (45 + 20 + 3) ÷ (160 + 20 + 3 + 2) = 68 ÷ 185 = .368.
Frequently asked questions
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Sources
- MLB.com — On-base Percentage
- MLB.com — Standard & Advanced Stats Glossary
- FanGraphs — Sabermetrics Library
- Baseball Reference — Glossary
Last reviewed March 1, 2025. Rules and manufacturer charts change — verify against current official sources each season.