You start right here! On ruter.dk you find a description of each route, and you can plan your cycling trip using the maps that also show relevant points of interest such as accommodation, catering etc.
A good rule of thumb is to assume that you cycle about 12 km/h on average incl breaks. If you set off right after breakfast, you will often be able to cover 30-40 km before lunch and twice that before dinner. Of course, it all depends on how many stops you make along the way. And maybe the whole purpose of your trip is to visit a certain museum on your way and spend a good amount of time there.
We recommend planning with a little air in the program. It is a pity to pass by a nice view, a good beach or an exciting museum and not have the time to enjoy it. And it’s not funny if you must bike far in very bad weather or if the bike or your legs won’t cooperate.
If you are going on your first overnight trip and haven’t been a scout for ages, you can make it a little easier for yourself by choosing to sleep indoors in a hotel, hostel or similar. You can carry much less luggage, and you won’t have to set up a camp when you arrive at your destination. Instead, you can flop down in a chair.
Another tip is to plan with the public transport. If you are going on a day trip, maybe you can take a train or a bus some of the way. This option can also take you outside the immediate area. And on a longer multi-day trip, public transport can be an ideal way to get back to the starting point.