The 25-year-old will line up in the final alongside five-time Olympic champion Ryan Lochte and Russian Danila Izotov, the quickest from the semi-finals in 1:45.84minutes.
Renwick's own time of 1:46.95 was almost a second slower than his, and Britain's, record time of 1:45.99, and the Scot claims he will have to break it again to finish on the podium in Barcelona.
"I'm really happy with the result and I've got a good lane for the final and I'm really hoping the guys can pull me out in the first 100m as I just seem to be lacking a little bit there," said Renwick.
"If I can then really work that 200m then who knows what could happen in the final but it is going to be a close race that is for sure.
"I will need to break it [the British record] in the final, I was a bit disappointed I didn't get it in the semis.
"I felt absolutely fantastic in the warm up so I think I just overcooked it a little bit on the third 50m. I will have to rethink my tactics for the final."
Meanwhile Chris Walker-Hebborn won't be competing in the 100m backstroke final but he has vowed not to miss out over double the distance in Barcelona.
The 23-year-old's semi-final time of 53.96seconds was only good enough for sixth in his heat and 12th overall.
But attentions will now turn to the 200m backstroke which starts on Thursday, while the 4x100m medley relay also offers him a chance of redemption.
"It's nice to go under 54 seconds again but it's not enough to bring me back here for the final, so I'm a little bit gutted," he said.
"I've still got my main event to come, so I've got to brush myself down and get on with it and get my head into a different gear."
Britain had two finalists in the women's 200m medley but Sophie Allen and Siobhan-Marie O'Connor will be disappointed with their seventh and eighth place finishes respectively.
O'Connor, who only made it through following Australian Emily Seebohm's late withdrawal last night, started well and was second at the halfway stage but finished in 2:12.03 while Allen clocked 2:11.32.
Elsewhere, Lauren Quigley also made a semi-final exit in the women's 100m backstroke but her time of 1:00.96 has laid the foundations heading into the 50m and 200m later in the week.