The Collaborative International Dictionary of English v.0.48:

Miscalculate \Mis*cal"cu*late\, v. t. & i.
   1. To calculate erroneously.
      [1913 Webster]

   2. To judge wrongly, especially about the effects of action
      or the likely course of events.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

miscalculate
    v 1: judge incorrectly; "I had misestimated his determination"
         [syn: miscalculate, misestimate]
    2: calculate incorrectly; "I miscalculated the number of guests
       at the wedding" [syn: miscalculate, misestimate]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "miscalculate":
   deviate, discount, disregard, err, fall into error, go amiss,
   go astray, go awry, go wrong, judge amiss, lapse, misappreciate,
   miscompute, misconjecture, misconstrue, miscount, misdeem,
   misesteem, misestimate, misevaluate, misinterpret, misjudge,
   misread, misreckon, misthink, misunderstand, misvalue,
   overestimate, overlook, overprize, overrate, overvalue, slip,
   slip up, stray, stumble, trip, underestimate, underprize,
   underrate, undervalue, wander