Don't even try to measure your insole, you´ll never get it right. Just look at the measurements on any of your sneakers in CM or CHN. Then take that information and find the corresponding US size in the size guide. For example, the insole length of 25 CM corresponds to US 7 in Vans. You may get a different US size with a different brand due to slightly different measuring.
Fila, one of the largest brands of sportswear and footwear, was founded in Italy in 1911. The Fila brothers opened a women's and men's underwear shop in order to sell it to local residents. Later they opened a textile factory and expanded into the world.