approximately how many centimetres should your feet be for it to be size a 7 (40) and the same for size 8 (41)

Answer 1

The formula used by the EU is:

shoe size (mm) = (foot lenght+20 mm)/6.67

so your size 40 is 246.8 mm

40= (fl-20)/6.67
(40*6.67)-20=fl