The simplest way to find out your partner's ring size is to ask them directly. However, if you want to keep the proposal a surprise, you might need to be creative with your questioning. You could ask about ring sizes in general or ask them to try on a ring that you already have.

You can also borrow one of your partner's rings and bring it to us to get it sized. Make sure it's a ring that they wear on the ring finger of the hand you plan to propose to ensure an accurate measurement.

Another option is to trace the inside of one of your partner's rings on a piece of paper or use a ring sizing chart to determine the size. Again, make sure it's a ring that they wear on the ring finger of the hand you plan to propose to ensure an accurate measurement.

If you don't want to give away the surprise, you can ask one of your partner's friends or family members to help you. They may have an easier time finding out the ring size without raising suspicion.