Im trying to make my logo bigger for my website but it just keeps coming out small whatever i do. He

I just learnt to use Adobe Illustrator , the basics anyway. I am able to manipulate the size of the logo to almost scale in Illustrator. However, when I save the logo in JPEG/PNG for the web its always coming out smaller than i would like it to and i cant seem to get it to the size i want. Plz help me.