| Weld design | Throat area of butt weld A [mm 2 , in 2 ] | |
| for full weld length | for load-bearing (active) weld length | |
| 
 | A = s L | A = s (L - 2 s) | 
| 
 |  |  | 
| 
 | A = s L | A = s (L - 2 s) | 
| 
 | A = π s (D - s) | - | 
Meaning of used variables:
| D | tube outer diameter [mm, in] | 
| L | weld length [mm, in] | 
| s | thickness of thinner joined part [mm, in] | 
| δ | weld direction angle [°] |