Your website visitors are using many different screen sizes to view your business so it goes without saying that your site must look good on all of them.
Of course google analytics will tell you what percentage of visitors use a certain size screen and there are a number of online tools that will replicate your site for the different sizes.
One of the most accurate and my favourite is the responsive tool from chrome developer tools.
The tool comes with presets of the most popular devices and there is an option to add your own.
Just go to the 3 small dots in the top right hand corner of the chrome browser and select More tools and then Developer tools.
You will then see the options to change device sizes at the top of the screen.
I have made a short video below please take a look!
For more information on using chrome developer tools click here.