What is the optimal size for logos to place at the top of my form?

What size do you suggest I make my new logo for my form so its responsive on all devices? 

Thank you! I love JotForm! 

There really isn't a recommend size for logos in forms.  It would depend on the size of the form, where the form is being added, the contents of the image and various other factors.

Generally, I would say for header/logo image to make them slightly smaller than the total width of the form keeping in mind that the logo with be shrunk a fair amount on mobile. 

If you need any assistance getting things adjusted the way you would like, let us know and we will be happy to help.