No, you need to get fitted somewhere else. I've heard a lot of stories of VS not giving the right size. The only way you can really tell is if you try on the bra. There are guides out there, but a lot of them are wrong. They put me at a 30-32 A when I'm actually a 32C (30D might fit better, but bras are difficult to find in that size).
If you want to measure yourself, take the measurement of your underbust (around your right under your breasts) and then take the measurement of your bust (around your breast). Take the difference between your underbust measurement and bust measurement, and that determines your cup size. So a difference of one inch is an A cup, a difference of 2 inches is a B cup, etc. Then take your underbust measurement and add 4. The nearest even number should be your band size. This isn't 100% accurate, but it should give you a good idea of where to start looking. A lot of places take the difference between the underbust and bust after adding the 4 inches, which gives a cup size that's too small. My underbust measures 26 inches and my bust measures 30 inches, so I should be a 30D. Unfortunately it's nearly impossible to find bras in that size unless I want to spend a ton of money, so I move up to a 32C. It's the same cup volume but a larger band size, so I have to use the second hook instead of the first.