website design - Should forms be aligned left or center, if less than full page width?

Our web application has a small header and nav menu at the very top, and below, there is simply a large area of open space. We have no need for an always-present sidebar, so there is just one column. The layout is 100% window width, so it allows those with wide screens to use as much space as possible.

Our issue is that there are often times where certain one-page forms are very small and don't need to take much space. And the form can sometimes look awkward in the potentially huge open space below the header.

For instance, the password reset form below only requires two inputs. It is awkward to make the form 100% of the page width, so we kept it fairly narrow. But then, there is a ton of white space that isn't filled.

I feel that a narrow form should be centered, so there is equal white space on each side, and so you don't have to move your head away from the center of the screen.

But a co-worker feels that a narrow form should be left-aligned, because most everything else (like blocks of text) is left-aligned.

What do you guys think? Are there any principles or guidelines to follow for how to align entire forms? I've found tons of info on how to align labels, buttons, etc., but not on how to align forms when they don't take up the whole page.

The form - centered,

The form - left-aligned,

Answer

When the form is too far off to one side it emphasises the fact that it doesn't fill the page more than it would if it were centred. And drawing attention to that element would be drawing attention away from the form that you want to be the focus.

So I would suggest having the form centred.

However I would also suggest not having a stark white background. Try using a subtle pattern, or even just a light grey or off-white colour for the background, which will help draw attention more to the form.