Keep in mind that when you’re creating your banner, you want to prepare for the largest display size possible. If it looks great at 1600 x 400, it will look great on every display smaller than that too. And in order to prevent awkward cropping or image stretching, you want to design your banner with these dimensions in mind from the start.

Snappa can help you here, with the ability to create custom graphic sizes right from the get-go.

How to create a custom banner size in Snappa