Shotgun Gauge to Bore Diameter Converter
Convert shotgun gauge to bore diameter & cross sectional area instantly using our free online calculator tool.
Select a gauge measurement from the menu below to view the corresponding Bore-Diameter and Cross-Sectional area. Both inches and millimeters are displayed.
| Gauge | Diameter (in) | Diameter (mm) |
|---|
| Gauge | Area (in²) | Area (mm²) |
|---|
How to convert shotgun gauge to bore diameter
- Scroll to the top of this page to find the converter tool.
- Select the gauge value you want to convert (4, 8, 10, 12, 16, 20, 28 & .410 bore) .
- Read the diameter reading from the tool. It automatically updates as you change the gauge value.
- Read the cross-sectional area reading if needed – this also updates automatically.
- This page also has reference tables for all conversion rates if you prefer to use those.
What is shotgun gauge?
Shotgun gauge is a historic measure indicating how many lead balls of the bore’s diameter make up one pound. It helps hunters, shooters and gunsmiths choose the right ammunition and understand how size relates to recoil and patterning.
What is bore diameter?
Bore diameter is the internal width of the shotgun barrel, usually expressed in inches or millimetres. Converting between shotgun gauge and bore diameter clarifies which shells will chamber correctly and how shot patterns behave.
| Gauge | Diameter (in) | Diameter (mm) |
|---|---|---|
| 4 | 0.835 | 21.21 |
| 8 | 0.695 | 17.65 |
| 10 | 0.642 | 16.31 |
| 12 | 0.729 | 18.52 |
| 16 | 0.662 | 16.82 |
| 20 | 0.615 | 15.62 |
| 28 | 0.550 | 13.97 |
| .410 | 0.410 | 10.41 |
Who might need to convert gauge to diameter?
Hunters, reloaders, gunsmiths, educators and online sellers often convert shotgun gauge to bore diameter. For reloaders and gunsmiths it matters for safety and accuracy; for content creators and sellers it helps present clear product details to buyers.
Use cases of a gauge to bore diameter tool include…
Safety purposesMatch ammo to barrel size.
Reloading purposesDesign proper loads and wads.
Product listing purposesShow gauge and bore diameter for customers.
Convert between shotgun measurements now
Use our shotgun gauge calculator tool to convert gauge into shotgun bore diameter instantly. The tool provides measurements in both inches and millimeters.