How do I know the length of my vagina and how do I measure it?

You can actually measure it with your fingers!

The vagina ends to cervix, so you test the height with your fingers. If you can reach it easily, it is low. This means the size 1 might fit you better because it is shorter than size 2. If you can barely reach it or won't reach it at all, it is high.

Everyone is different and there isn't right or wrong answer for the length of vagina. The cervix can also move during the cycle and normally it lowers when the period starts.