What to do when the reference images are different sizes?

I’ve tried with photoshop but cant seem to resize the image to match the other one. I’ve been trying to make the smaller version bigger, but nothing happens when I save the image, so what do I do?

Sometimes you get reference images that just won’t line up, no matter what you do. They just are not drawn as a compatible set. If scaling the x and y dimensions of the background image don’t get the two views to line up, what I usually do is decide which one to use for precise measurements, and just use the other image for dimensions that aren’t available in the first one.

For example, if you are trying to model a head, and you get the chin and eyes to line up in front and side views, but the nose just won’t line up without throwing the other things off: decide to use the side view, for example, for the heights on the nose, even if it’s off in the front view, and just use the front view for the nose widths, which you can’t see in side view.