On-Base Percentage Calculator
Calculate OBP from hits, at-bats, walks, hit-by-pitches and sacrifice flies, with the exact denominator and three-decimal display.
Calculate on-base percentage using the five counts that enter its standard formula. The numerator credits hits, walks and hit-by-pitches; the denominator also accounts for at-bats and sacrifice flies. This tool keeps the denominator visible so you can check that the inputs cover the same player and period.
How to use this tool
- Use official scoring counts from one consistent period.
- Enter whole-number totals; include home runs in total hits.
- Check the walk, hit-by-pitch and sacrifice-fly counts.
- Read the conventional display and inspect the supporting counts.
Formula
OBP = (H + BB + HBP) / (AB + BB + HBP + SF)
Use official event counts. Sacrifice bunts and awards for interference, obstruction or a shift restriction violation are excluded from this formula. An event should not be counted again as an at-bat when the official scoring excludes it.
Example
With 30 hits, 100 at-bats, 10 walks, 2 hit-by-pitches and 3 sacrifice flies, the numerator is 42 and the denominator 115. OBP is 42 ÷ 115 = 0.365217…, displayed as .365.
Reading the result
A rounded rate summarizes the supplied sample. This page does not determine championship eligibility or account for opponent quality. Keep numerator and denominator totals when combining records instead of combining rounded display values.
Frequently asked questions
Can OBP be calculated with zero at-bats?
Yes, if other qualifying events make the denominator positive. One walk with zero at-bats and no other events gives 1 divided by 1, or 1.000.
Do errors and a fielder’s choice count as reaching base here?
They do not add to this numerator. Use the official H, AB, BB, HBP and SF counts rather than every occasion on which the batter stood on a base.
Can I average OBP values from two periods?
Combine their component totals first. An unweighted average of two rates is wrong when their denominators differ, and rounding each period can introduce another difference.
Sources
Last updated: 2026