How do I determine if the replacement property is of “equal or lesser value” than the original?

This depends upon the timing of the purchase or completion of construction of the replacement property. In general, “equal or lesser value” means the fair market value of the replacement property does not exceed one of the following:

100% of the market value of the original property, if the replacement property is purchased or newly constructed before the original property is sold.

105% of the market value of the original property, if the replacement property is purchased or newly constructed within the 1st year after the original property sold.

110% of the market value of the original property, if the replacement property is purchased or newly constructed within the 2nd year after the original property sold.

Have a wonderful day and please let me know if you need anything.