4.3.3 Ring finger 5/16" rule

4.3.3   measurement 

 The ring finger span is often derived from the middle finger span rather than measured independently, using the 5/16" Ring Finger Rule . Spectre Cloud can apply this calculation for you through Auto-Calculate Ring Span (2.6.8) , or you can enter the ring finger span manually. 
 📐 The Rule 
 The ring finger span is calculated as: 
 Ring Finger Span = Middle Finger Span + (5/16" − d) 
 Where d is the observed difference between the second joint lines of the middle and ring fingers, measured with the bowler's hand flat on the ball. When the joint lines are level ( d = 0" ), the ring span comes out 5/16" longer than the middle span; as d increases, the ring span shortens relative to the middle. 
 d value Adjustment (5/16" − d) Effect on ring span 0" +5/16" Ring span 5/16" longer than middle 5/16" 0" Ring span equals middle span > 5/16" Negative Ring span shorter than middle 

 ⚙️ Auto Calculation in Spectre Cloud 
 When Auto-Calculate Ring Span is used: 
 
 Enter the middle finger span as measured. 
 Enter the d measurement in its field. 
 Spectre Cloud calculates and displays the ring finger span using Middle Span + (5/16" − d) . 
 Review the result before saving. 
 
 ⚠️ Verify with your Spectre team: confirm the exact field label for the d input and whether the calculated ring span is read-only or an editable value the operator can still override. 
 ✏️ Manual Entry 
 If you measure the ring finger span directly, you can enter it manually instead of using the calculation — appropriate when you have independent measurements of both fingers, or when transferring an explicit ring span from a legacy sheet. 
 Related Sections 
 
 4.3.1 — Entering span measurements 
 4.4.5 — Inputting pitches 
 2.6.8 — Auto-Calculate Ring Span (the 5/16" rule) 
 05 — Oval Calculator 
 
 Tip: The 5/16" rule produces a starting span, not a fixed prescription. If a bowler reports the ring finger feels consistently tighter or looser than the middle despite a correct-looking sheet, re-check the d measurement first — it takes under a minute and often explains the complaint.