When you have two types of tire measurements, "Old-style" and ERTRO, listed on a bicycle tire, use ERTRO to calculate wheel circumference.
ERTRO measure notation: "tire width"-"rim diameter", since my bicycle tire size is listed as 26 x 1.75 American & 47-559 ERTRO, I will use 47-559 in the following formula:
Circumference = [(2 x tire width)+ rim diameter] x pi
Circumference = [(2 x 47) + 559] x 3.14159265359
Circumference = [94 + 559] x 3.14159265359
Circumference = 653 x 3.14159265359
Circumference = 2051.46000279 mm
Therefore, I would enter 2051 mm in my Bell F12 bike computer as the wheel value/circumference.