Am I ready for a century? I've just learned of a local century ride that is only 2 weeks away. I'd like to join, but not sure if I'm ready. I've been commuting by bike for the last five years. The last year of my commuting has been 18 miles/day that I do at least 4 days/week. Over the last 2 months, I've done several weekend rides of 40-50 miles, but I haven't gone over 50. I usually take one 10-minute break at about the 75% mark during these longer rides. After these longer rides, I'm tired and hungry, but feel like I could keep going at a leisurely pace after eating. Am I ready to leap to 100 miles? I don't have any days between now and the event where I'll be able to go for more than about a 30-mile ride.

The terrain for the century is flat, just like my normal biking.
Its not the distance, its the time on the bike.

Assuming this is not a solo ride, you'll be riding with other people either in a proper rotating bunch ride, or just on the same road/direction as them.  This alone will increase your overall speed by as much as 20%.

If you can be seated on a bike for 6 hours in a day, you can do this ride.

You will need to eat regularly.  For me thats "something" every hour, a gel or chocolate or a bar or some sort.  Or bananas, some people like them.

Water is also big - One plain water bottle and one with electrolyte mix added.  You will be able to top-up water bottle at the filling stations, for 161 km I'd expect 3-5 total stations along the route.  Check the map, but plan for one to be missing - its happened to me.

Filling stations are a rest point - you can get off the saddle while doing bottles, drink and eat, and go again.  Personally, 5 mins is plenty, but on a really long ride I like a 15 minute at somewhere over 50%.