# 4.3.3 Ring finger 5/16" rule

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<span style="font-family: monospace; color: #6b7280;">4.3.3</span> <span style="border: 1px solid #d1d5db; color: #4b5563; padding: 2px 8px; border-radius: 3px; font-size: 0.85em;">measurement</span>

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.

<table id="bkmrk-d-valueadjustment-%285"><thead><tr><th>d value</th><th>Adjustment (5/16" − d)</th><th>Effect on ring span</th></tr></thead><tbody><tr><td>`0"`</td><td>`+5/16"`</td><td>Ring span 5/16" longer than middle</td></tr><tr><td>`5/16"`</td><td>`0"`</td><td>Ring span equals middle span</td></tr><tr><td>`> 5/16"`</td><td>Negative</td><td>Ring span shorter than middle</td></tr></tbody></table>

## ⚙️ Auto Calculation in Spectre Cloud

When Auto-Calculate Ring Span is used:

1. Enter the **middle finger span** as measured.
2. Enter the **d measurement** in its field.
3. Spectre Cloud calculates and displays the ring finger span using `Middle Span + (5/16" − d)`.
4. 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.