Upvote:2
For a journey between the airport and Helsinki central, you will require a 'Regional' type ticket (see the HSL website for further information on what different ticket types cover)
At the current date, the single price for this journey is β¬5 if bought from a ticket machine (the website linked above states that these do accept cards with a chip) or β¬4.20 if you download the HSL app and buy the ticket there (I used the app as a tourist on my last visit to Helsinki). The ticket will be valid for 90 minutes from the time of purchase.