How to Use the Shape Area & Perimeter Calculator
Select a shape and enter its dimensions to instantly calculate area and perimeter. Supports circle, rectangle, square, triangle (base+height or Heron's formula), parallelogram, trapezoid, rhombus, ellipse, regular pentagon, and regular hexagon.
Key Formulas
Circle: Area = πr², Perimeter = 2πr
Rectangle: Area = w×h, Perimeter = 2(w+h)
Triangle: Area = ½×base×height (or Heron's formula)
Rhombus: Area = d1×d2÷2 (d1, d2 are diagonals)
FAQ
Is the ellipse perimeter exact?
Ellipse perimeter has no simple closed form. This calculator uses the Ramanujan approximation: 2π√((a²+b²)/2), accurate to within ~1% for most shapes.
What happens if the three sides can't form a triangle?
If the sum of any two sides is not greater than the third, the triangle is impossible. An error message is displayed.