updated 02/04/2011 AT 12:15 PM ET
•originally published 02/04/2011 AT 12:30 PM ET
The couple got engaged in November, but Lachey admits he’d been planning it for a while.
“You gotta take it in stages. If you set the bar too high then you set yourself up for failure,” Lachey tells Entertainment Tonight of his proposal. “This was a carefully calculated plan. You have to set the romance, but you have to take it in phases.”