Sometimes damages are difficult to calculate with certainty so the courts are left to estimate. For example, in the case of Fera v. Village Plaza (396 Mich. 639, 242 N.W.2d 372 (Mich. 1976)), Village Plaza (a landlord) signed a lease with Fera for a bookstore, and then reneged on the lease. While Fera obviously suffered damages from loss of business, how could the court calculate the magnitude of the loss, since the business never opened? The Court found that it is not necessary to show what the damages are "with certainty", but only that the plaintiff, "lay the basis for a reasonable estimate of the extent of the harm measured in money." It is impossible to know how much money Fera would have made, but it is possible to get a good estimate based on profits from similar businesses and other economic data. That's close enough.