It appears the same to me as your screenshot, I'm at 100%.
But this is too big, compared to normal websites. Almost twice as big. I can barely see 3 posts of the homepage on screen. Even as I type this, I will have to scroll down to get to the submit button (which too is massive).
Needing to scroll too much is a bad user experience. I don't know how familiar you are with web dev, but you need responsive CSS. That way, everything on screen renders at normal size (normal being what we see on YT, facebook, etc.) on all screen sizes.
Check out any of the free bootstrap themes that will do this automatically for you -