What is a Good On-Base Percentage?

With today’s focus on on-base percentage stronger than at any other time in baseball history, it got me thinking — what exactly is a good OBP? I mean, we know Barry Bonds’s .609 in 2004 was abnormally superb, and Ike Davis’s current .236 is really bad. And we know .400 is very good, but what is the cutoff point? I decided to do some digging.

I figured we needed to compare it to a number with which we are already familiar. I chose batting average, since the two stats are closely related anyway. We know .300 is the gauge — if a player is hitting .300 or above, he is very good. The further he slides down from .300, the worse he is. So I decided to come up with an OBP number that could be the equivalent to a .300 batting average — above that number is very good, and the further a player slides below, the worse he is.

I began by looking at all-time MLB stats. Around 200 players have career batting averages of .300 or better. Then I looked at career on-base percentage. I went down to the 200th ranking, and the number was around .370. Then I looked at last year’s batting statistics. Twenty five players batted .300 or better. And guess what? The 25th ranked OBP was — you guessed it — around .370.

So .370 appears to be the number. That means if a player has a .370 on-base percentage, it is the equivalent of batting .300, so we know he is among the elite. A .400 OBP would be equal to .330, so very good indeed. On the other side of the scale, if a player as a .350 OPB, that is as if he is hitting .280, which is still all right. However, if he has a .300 OPB, it is like hitting .230, which is not very good at all.

I’m sure I’m not the first person to come up with a formula like this. I have no idea how other people figured things, but this is the formula that I will be using to make sense of on-base percentage.