I agree with Suezq. If you're not comfortable with just eyeballing the widths and feel like you need some help, the Fibonacci Sequence (also known as the Golden Ratio) would be a great resource.
To understand the concepts easily, watch this fun Donald Duck 30-minute video.
https://www.youtube.com/watch?v=PvceKeHl0Sg
If you want to skip to the good stuff and see how it can be used in quilting, see the following links. (I googled "fibonacci sequence in quilting" if you wanted to check out more links.)
https://www.jinnybeyer.com/blog/the-...-golden-ratio/
https://www.jinnybeyer.com/blog/fibo...-golden-ratio/
https://prezi.com/gztzw-gtwupl/quilt...mber-sequence/
http://doyoueq.com/forum/viewtopic.php?f=4&t=453