United Kingdom Size 40 to US: 34

United Kingdom Size 40: Corresponds to a waist size of 100 $\text{cm}$ (40 $\text{in}$), total strap length of 115 $\text{cm}$ (45.3 $\text{in}$), and recommended fit classification Relaxed / Comfortable.

US: 34: Corresponds to a waist size of 85 $\text{cm}$ (34 $\text{in}$), total strap length of 100 $\text{cm}$ (39.4 $\text{in}$), and recommended fit classification Standard / Regular.