If you got some information about your area, the question is how to calculate the other informations. In many cases this is possible. A square or a circle e.g. are already given by  a single information (e.g. perimeter or area). Having areas with less symmetries means we need more information. Mathepower has many area calculors.   
  
  Calculators for that topic:   
    
Triangle calculator
 
Circle calculator
 
Arc calculator
 
Rhomboid calculator
 
Square calculator
 
Rhomb calculator
 
Rectangle calculator
 
Trapezoid calculator