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