https://en.wikipedia.org/wiki/Canon_EOS_550D says your max output resolution is 5,184 × 3,456 so assuming you want the largest print for that roll width, you'll get about 83 pixels per linear inch, or 3.2 px/mm, 0.3mm/px.
@Emyr started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
https://en.wikipedia.org/wiki/Canon_EOS_550D says your max output resolution is 5,184 × 3,456 so assuming you want the largest print for that roll width, you'll get about 83 pixels per linear inch, or 3.2 px/mm, 0.3mm/px.