What Do All Of The Numbers Mean When Buying A Bowling Ball

Know What The Numbers Mean When Buying A New Bowling Ball

By BowlersMart IQ Metro Detroit Head Instructor – Mike Calhoun

We all have looked at a bowling ball sales sheet or shelf talker trying to check the weight block picture, see what kind of coverstock the ball has, or even have a diagram of the characteristic / generic path of motion that particular bowling ball has. Now with that being said, there are also numbers on the shelf talker, one being the RADIUS OF GYRATION or (RG), DIFFERENTIAL (Diff), INTERMEDIATE DIFFERENTIAL (which is only on your asymmetrical bowling balls). Here is some information to help you understand the bowling ball characteristics and how these will benefit you and the motion you desire.



HIGH RG:2.57-2.60

MEDIUM RG: 2.54-2.56


Higher the RG numbers will tell us that the bowling balls mass is concentrated more towards the cover, so we tend to use the term “cover heavy”, and in return means the bowling ball has length through the heads(front part of the lane).
Lower the RG numbers tell us the opposite and the bowling balls mass is concentrated to the mass of the core or “core heavy”, which means the bowling ball will tend to see the front part of the lane. So in layman’s terms, it will transition earlier.




MEDIUM DIFF:.049-.040


The differential is defined as the difference between the maximum and minimum RG. So the DIFFERENTIAL tells us the bowling balls flare potential (or overall hook). This measurement determines the flare potential as a rating of high, medium, low.


Sometimes there is another number on the shelf talker and is referred to as the INTERMEDIATE DIFF; (Located on your asymmetrical bowling balls) This is the difference between the (Y) AXIS and (Z) AXIS (intermediate diff) So the higher the INTERMEDIATE DIFF the stronger the bowling balls PSA (preferred spin axis) or mass bias is.
Key factor here is these are only reference numbers and before drilling, and as soon as the balls are drilled these numbers can increase or decrease. Well i hope you learned and now have a better understanding about the numbers.

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6 thoughts on “What Do All Of The Numbers Mean When Buying A Bowling Ball

  1. Pamela Adams says:

    I am getting 2 – 14 lb balls. One is the Venom and one is the Radical Trailer Blazer. The Venom had an RG of 6; the Trail Blazer is an RG of 8.5.
    I want both finger tip drilled.
    I’ve never rolled a finger tip ball,
    Which is why I went with a lower RG and a higher RG.
    I mostly bowl as a straight roller. I currently roll a12 lb ball at between 15 and 16 mp
    Please let me know what you thinkh.

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