KEY: Calamity.
SYN: Disaster, misfortune, mishap, catastrophe, misadventure, trouble, visitation, affliction, reverse, blight.
ANT: godsend, blessing, boon.
=
KEY: Calamitous.
SYN: Disastrous, illfated, fatal, unlucky, hapless, unfortunate, inauspicious, troublous, illstarred, ill-omened.
ANT: Felicitous, fortunate, auspicious, favorable, propitious, advantageous.
=
KEY: Calculate.
SYN: Estimate, consider, weigh, number, count, apportion, proportion, investigate, reckon, rate, compute.