If you want to make a surprise on the day of proposal, you can hide your girlfriend and steal to the jewelry store to buy a ring. But before that, you have to find out your girlfriend's finger size so as not to wear it too loosely or too tightly. In both cases, the ring can not be worn normally in the future, and the effect of a token of love can not be achieved.

You can quietly get the size of your partner's ring in your daily life, for example, try it on in a gold shop when you are shopping, and then measure it after the other person falls asleep, and buy a best friend to take her to the gold shop to try it on. These methods are indirect to obtain specific values, and will not make the other party feel their purpose.