To get oriented, put your RMS meter on the track you want to want yours to sound like (more or less). Listen to a full, loud portion of the song and take a look at the Average RMS:

Picture 5

Now, put the meter on your own song and take a reading. Let’s say the unmastered song shows an average RMS of -19. That would mean we have an approximately 10dB defecit to make up.

Just for laughs, let’s dive right in and make up the gain using Limiter:

Picture 7

You can use the meter to fine tune this, but don’t spend too long with that. Switch over to using your ears. A/B the tracks and give a good listen. The loudness is probably in the ballpark now.

Pay close attention and you may find that even matching the RMS level very closely, your mix still doesn’t sound as loud. This may be because the track you’re comparing yours to is exceptionally well mixed, or has been mastered by a professional who has other tricks for maximizing the apparent loudness.

Don’t be fooled into thinking you just need to add more limiting. You’ll just end up making things worse.