Diamond Engagement Rings are the gift of a lifetime for some one you love. It is a token of love for the special lady in your life who by accepting this ring will be known as your wife. It’s a comitment for a lifetime.
Diamonds are very close to a women’s heart. So while choosing a ring special care needs to be taken. It’s better to take your lady to the jewelry store and let her choose it rather than shopping it yourself. If you are very confident about her finger size than its fine but possibility of difference in size can be there. It’s not necessary what you may think about her finger or ring size that may be correct.
But if you want to surprise her than you will have to take that extra risk or else you can tactfully get any ring she wears and go ahead and give the size of that ring.