The simplest way to reach the island is by car or coach. If travelling by car from Zagreb the quickest way is to take the highway until Rijeka and from there reach the island by crossing the Krk bridge – Krčki most. The pay toll will cost you 15 Euros, but you can take alternative routes to save on money. More information on other road routes and road conditions you can find here. If you are coming from the Slovenia direction choose the border crossing Rupa and continue in the Rijeka direction. If however you are arriving from Italy then you will enter Croatia through the border crossing Kozina and should continue driving towards Rijeka. From the directions of Hungary and Czech Republic first you will have to reach Zagreb and then Rijeka over Karlovac.
If you are travelling by coach you can reach Rijeka with direct lines from all bigger Croatian cities: Zagreb, Split and Osijek and then take a coach from Rijeka to travel further for Krk. More information on timetables and prices you can find on the web pages of Autotrans Rijeka. On the same page you can find out more information on how to get to Trieste, Munich and other European cities with which Rijeka is connected. Settlements on Krk are connected amongst each other with local coach lines and more detailed information you can find out on the web pages of Autotrans Rijeka.
If you are on the Zagreb-Rijeka train you will have to continue your journey to Krk with a coach from the main Rijeka coach station. A train ride from Zagreb to Rijeka will take 4,5 h of your time and will cost you 15 Euros. Timetable of this route is available here.
If you are arriving from abroad then the best option is to travel by plane since there is an airport located on the island in the vicinity of Omisalj. In season, except for Frankfurt, the airport is also connected with 15 other European cities (London, Stuttgart, Stockholm, Frankfurt, Oslo). More information on flight schedules find on the web pages of the airport or take a look at the pages of some of the airlines that fly to Krk.
With regular boat lines it is possible to arrive from Cres and Rab. Timetables for the Valbiska (Krk) - Merag (Cres) line see here and for the line Valbiska (Krk)- Lopar(Rab) here. Ticket price for the route Valbiska – Merag is 2,5 E for adults and for children between 3-12 years it is half price and children younger than 3 travel for free. Car transport will cost you 30 Euros. Since Krk has marinas you can also arrive in your own arrangement with a yacht or a sailboat.