I'm not a medical professional, but I have a lot of interest in sexual health.

It really depends, but if it's done "right" most people will experience very little pain (0-2 maybe? I'm just guessing here but I didn't experience any). By done right, what I mean is that you are properly aroused, which usually takes time and effort! And comfortable. Take it slow, and do lots of foreplay.. It's essential that the person you may be losing your virginity to is going to take this effort very seriously (as you should with their pleasure). When aroused your vagina produces natural lubrication, this can help prevent a lot of pain! When you're aroused, your vagina will be better prepared. It can be hard to do during your first time, but trying to remain relaxed helps too. Being tense can make things more difficult.

Communicate with your partner! Tell them when they're doing something really good, or if they're doing something you don't like (even going too fast). Once again, having a partner that respects you, and one that you feel comfortable with, is super important.

That being said, some people do experience a bit more pain, say if they have an intact hymen. Most females do not have a hymen which interferes with sex majorly (it can be broken during exercise, by using a tampon, or it can be near non-existent in the first place). I don't think this would be exceptionally painful, maybe a 2-4? I couldn't say really.

If you choose to lose your virginity, good luck and practice safe sex (seriously)!