I ask this because I want to buy bras for my wife as a surprise. I want to get something that I like and she would never get. I had never asked her her bra size before. Today as I was going through her drawer I was shocked to see that her sizes are all over the place.
Bras are a very tricky item to buy as gift. But since you want to venture into that territory you should be aware if a few facts. The number should not vary but the cup
Size could. The padded and push up bras make the bust look larger. The cute lacy bras rarely offer support. If she is using under wire bras then stick to the same type. so take one or two as an example with to the store with you. And try to not look like a creeper :-p
Not really - some bras are in US measurements and some use European. But most women are wearing the wrong bra size and don't want to get a bra fitting so they just buy many different bras until they get one that fits. Also if you lose or gain weight, your bust size changes. Maybe if she has more of one size you can try that size.