Having the standard resolutions used for video on the web is helpful. Here are a few articles on the subject, and handy reference image.

www.techgyd.com/video-resolution-difference
flexclip.com/learn/youtube-video-size.html

  • 3840 x 2160 – 4k
  • 2560 x 1440 – 2k
  • 1920 x 1080 – 1080p
  • 1280 x 720 – 720p
  • 854 x 480 – 480p
  • 640 x 360 – 360p
  • 426 x 240 – 240p